diff --git a/main/Base.lproj/Main.storyboard b/main/Base.lproj/Main.storyboard
index 34cc95e..a1691fc 100644
--- a/main/Base.lproj/Main.storyboard
+++ b/main/Base.lproj/Main.storyboard
@@ -461,6 +461,15 @@
                                                 <action selector="didClose:" destination="W5Q-oz-bFb" id="wyw-vo-6xL"/>
                                             </connections>
                                         </barButtonItem>
+                                        <barButtonItem key="rightBarButtonItem" id="bTi-7F-CFS">
+                                            <button key="customView" opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="infoLight" showsTouchWhenHighlighted="YES" lineBreakMode="middleTruncation" id="kqK-SL-CxZ">
+                                                <rect key="frame" x="279" y="16" width="25" height="24"/>
+                                                <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
+                                                <connections>
+                                                    <action selector="showInfoScreen" destination="W5Q-oz-bFb" eventType="touchUpInside" id="TuI-R9-PNr"/>
+                                                </connections>
+                                            </button>
+                                        </barButtonItem>
                                     </navigationItem>
                                 </items>
                             </navigationBar>
@@ -502,14 +511,14 @@
                                                     <nil key="textColor"/>
                                                     <nil key="highlightedColor"/>
                                                 </label>
-                                                <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" horizontalCompressionResistancePriority="300" insetsLayoutMarginsFromSafeArea="NO" text="Count" textAlignment="right" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="JWp-6l-HTJ">
-                                                    <rect key="frame" x="116.5" y="42.5" width="37" height="16"/>
+                                                <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" horizontalCompressionResistancePriority="500" insetsLayoutMarginsFromSafeArea="NO" text="Count" textAlignment="right" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="JWp-6l-HTJ">
+                                                    <rect key="frame" x="109.5" y="42.5" width="37" height="16"/>
                                                     <fontDescription key="fontDescription" style="UICTFontTextStyleFootnote"/>
                                                     <color key="textColor" systemColor="secondaryLabelColor" red="0.23529411759999999" green="0.23529411759999999" blue="0.26274509800000001" alpha="0.59999999999999998" colorSpace="custom" customColorSpace="sRGB"/>
                                                     <nil key="highlightedColor"/>
                                                 </label>
                                                 <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" insetsLayoutMarginsFromSafeArea="NO" text="5900" textAlignment="natural" lineBreakMode="clip" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="q5v-FM-iGo" customClass="TagLabel" customModule="AppCheck" customModuleProvider="target">
-                                                    <rect key="frame" x="157.5" y="39.5" width="32.5" height="21.5"/>
+                                                    <rect key="frame" x="150.5" y="39.5" width="42.5" height="21.5"/>
                                                     <color key="backgroundColor" systemColor="secondarySystemBackgroundColor" red="0.94901960780000005" green="0.94901960780000005" blue="0.96862745100000003" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                                     <fontDescription key="fontDescription" style="UICTFontTextStyleFootnote"/>
                                                     <nil key="textColor"/>
@@ -521,7 +530,7 @@
                                                     </userDefinedRuntimeAttributes>
                                                 </label>
                                                 <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" insetsLayoutMarginsFromSafeArea="NO" text="10.35s" textAlignment="natural" lineBreakMode="clip" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="zCg-I0-4Tz" customClass="TagLabel" customModule="AppCheck" customModuleProvider="target">
-                                                    <rect key="frame" x="265" y="39.5" width="40" height="21.5"/>
+                                                    <rect key="frame" x="255.5" y="39.5" width="49.5" height="21.5"/>
                                                     <color key="backgroundColor" systemColor="secondarySystemBackgroundColor" red="0.94901960780000005" green="0.94901960780000005" blue="0.96862745100000003" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                                     <fontDescription key="fontDescription" style="UICTFontTextStyleFootnote"/>
                                                     <nil key="textColor"/>
@@ -532,14 +541,14 @@
                                                         </userDefinedRuntimeAttribute>
                                                     </userDefinedRuntimeAttributes>
                                                 </label>
-                                                <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" horizontalHuggingPriority="750" horizontalCompressionResistancePriority="250" insetsLayoutMarginsFromSafeArea="NO" text="Divergent" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="T4X-cn-msT">
-                                                    <rect key="frame" x="202" y="42.5" width="59" height="16"/>
+                                                <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" horizontalHuggingPriority="750" horizontalCompressionResistancePriority="400" insetsLayoutMarginsFromSafeArea="NO" text="Diverge" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="T4X-cn-msT">
+                                                    <rect key="frame" x="205" y="42.5" width="46.5" height="16"/>
                                                     <fontDescription key="fontDescription" style="UICTFontTextStyleFootnote"/>
                                                     <color key="textColor" systemColor="secondaryLabelColor" red="0.23529411759999999" green="0.23529411759999999" blue="0.26274509800000001" alpha="0.59999999999999998" colorSpace="custom" customColorSpace="sRGB"/>
                                                     <nil key="highlightedColor"/>
                                                 </label>
                                                 <view opaque="NO" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="9Bb-e5-D3O" customClass="MeterBar" customModule="AppCheck" customModuleProvider="target">
-                                                    <rect key="frame" x="187" y="39.5" width="3" height="21.5"/>
+                                                    <rect key="frame" x="190" y="39.5" width="3" height="21.5"/>
                                                     <constraints>
                                                         <constraint firstAttribute="width" constant="3" id="wWb-VG-Kqa"/>
                                                     </constraints>
diff --git a/main/Common Classes/QuickUI.swift b/main/Common Classes/QuickUI.swift
index 8abf45d..1d70f6c 100644
--- a/main/Common Classes/QuickUI.swift	
+++ b/main/Common Classes/QuickUI.swift	
@@ -36,6 +36,8 @@ struct QuickUI {
 	static func text(attributed: NSAttributedString, frame: CGRect = CGRect.zero) -> UITextView {
 		let txt = self.text("", frame: frame)
 		txt.attributedText = attributed
+		txt.textContainerInset = .zero
+		//txt.textContainer.lineFragmentPadding = 0 // remove left right padding
 		return txt
 	}
 }
diff --git a/main/Common Classes/TutorialSheet.swift b/main/Common Classes/TutorialSheet.swift
index 845920a..0afc652 100644
--- a/main/Common Classes/TutorialSheet.swift	
+++ b/main/Common Classes/TutorialSheet.swift	
@@ -1,11 +1,18 @@
 import UIKit
 
-fileprivate let margin: CGFloat = 20
-fileprivate let cornerRadius: CGFloat = 15
-fileprivate let uniRect = CGRect(x: 0, y: 0, width: 500, height: 500)
+fileprivate var margin: CGFloat { 20 }
+fileprivate var sheetInset: CGFloat { cornerRadius/2 }
+fileprivate var cornerRadius: CGFloat { 15 }
+fileprivate var uniRect: CGRect { CGRect(x: 0, y: 0, width: 500, height: 500) }
 
 class TutorialSheet: UIViewController, UIScrollViewDelegate {
 	
+	/// Maximum displayable width of a Tutorial Sheet in portrait mode.
+	public static var verticalWidth: CGFloat {
+		let s = UIScreen.main.bounds.size
+		return min(s.width, s.height) - 2 * (margin + sheetInset)
+	}
+	
 	public var buttonTitleNext: String = "Next"
 	public var buttonTitleDone: String = "Close"
 	
@@ -105,7 +112,8 @@ class TutorialSheet: UIViewController, UIScrollViewDelegate {
 		}
 		let prev = content.subviews.last
 		content.addSubview(x)
-		x.anchor([.top, .width, .height], to: pageScroll)
+		x.anchor([.top, .height], to: pageScroll)
+		x.widthAnchor =&= sheetBg.widthAnchor - 2 * sheetInset
 		x.leadingAnchor =&= (prev==nil ? content.leadingAnchor : prev!.trailingAnchor)
 		lastAnchor?.isActive = false
 		lastAnchor = (x.trailingAnchor =&= pageScroll.trailingAnchor)
@@ -125,7 +133,7 @@ class TutorialSheet: UIViewController, UIScrollViewDelegate {
 		
 		pager.anchor([.top, .left, .right], to: sheetBg)
 		pageScroll.topAnchor =&= pager.bottomAnchor
-		pageScroll.anchor([.left, .right, .top, .bottom], to: sheetBg, margin: cornerRadius/2) | .defaultHigh
+		pageScroll.anchor([.left, .right, .top, .bottom], to: sheetBg, margin: sheetInset) | .defaultHigh
 		button.topAnchor =&= pageScroll.bottomAnchor
 		button.anchor([.bottom, .centerX], to: sheetBg)
 //		button.bottomAnchor =&= sheetBg.bottomAnchor - 30
diff --git a/main/Data Source/SyncUpdate.swift b/main/Data Source/SyncUpdate.swift
index 00d05f4..b806366 100644
--- a/main/Data Source/SyncUpdate.swift	
+++ b/main/Data Source/SyncUpdate.swift	
@@ -159,7 +159,6 @@ class SyncUpdate {
 					notify(insert: r, .Latest)
 				}
 			} else if range != nil {
-				// FIXME: removing latest entries will invalidate "last changed" label
 				if let r = rows(from(new!), to(old), scope: range!) {
 					notify(remove: r, .Latest)
 				}
diff --git a/main/Extensions/Font.swift b/main/Extensions/Font.swift
index 17c8f0f..43381e3 100644
--- a/main/Extensions/Font.swift
+++ b/main/Extensions/Font.swift
@@ -13,6 +13,14 @@ extension UIFont {
 	}
 }
 
+extension NSAttributedString {
+	static func image(_ img: UIImage) -> Self {
+		let att = NSTextAttachment()
+		att.image = img
+		return self.init(attachment: att)
+	}
+}
+
 extension NSMutableAttributedString {
 	static private var def: UIFont = .preferredFont(forTextStyle: .body)
 	
@@ -31,4 +39,13 @@ extension NSMutableAttributedString {
 		]))
 		return self
 	}
+	
+	func centered(_ content: NSAttributedString) -> Self {
+		let before = length
+		append(content)
+		let ps = NSMutableParagraphStyle()
+		ps.alignment = .center
+		addAttribute(.paragraphStyle, value: ps, range: .init(location: before, length: content.length))
+		return self
+	}
 }
diff --git a/main/Requests/Analytics/VCCoOccurrence.swift b/main/Requests/Analytics/VCCoOccurrence.swift
index 8997cc5..ec4e9fa 100644
--- a/main/Requests/Analytics/VCCoOccurrence.swift
+++ b/main/Requests/Analytics/VCCoOccurrence.swift
@@ -33,15 +33,24 @@ class VCCoOccurrence: UIViewController, UITableViewDataSource {
 		let domain = fqdn!
 		let time = Timestamp(selectedTime)
 		DispatchQueue.global().async { [weak self] in
-			guard let db = AppDB, let times = db.dnsLogsUniqTs(domain), times.count > 0 else {
-				return // should never happen, or what did you tap then?
+			let temp: [ContextAnalysisResult]
+			let total: Int32
+			if let db = AppDB,
+				let times = db.dnsLogsUniqTs(domain), times.count > 0,
+				let result = db.contextAnalysis(coOccurrence: times, plusMinus: time, exclude: domain),
+				result.count > 0
+			{
+				temp = result
+				var sum: Int32 = 0
+				for x in result { sum += x.count }
+				total = sum // if statement guarantees >= 1
+			} else {
+				temp = []
+				total = 1
 			}
-			guard let result = db.contextAnalysis(coOccurrence: times, plusMinus: time, exclude: domain) else {
-				return
-			}
-			self?.dataSource = result
-			self?.logMaxCount = log(CGFloat(result.reduce(0) { max($0, $1.count)  }))
 			DispatchQueue.main.sync { [weak self] in
+				self?.dataSource = temp
+				self?.logMaxCount = log(CGFloat(total + 1))
 				self?.tableView.reloadData()
 			}
 		}
@@ -72,7 +81,9 @@ class VCCoOccurrence: UIViewController, UITableViewDataSource {
 		cell.count.text = "\(src.count)"
 		cell.avgdiff.text = String(format: "%.2fs", src.avg)
 		
-		cell.countMeter.percent = (log(CGFloat(src.count)) / logMaxCount)
+		// log percentage of total co-occurrence count + 1 (min: log(2))
+		cell.countMeter.percent = (log(CGFloat(src.count + 1)) / logMaxCount)
+		// log percentage of selected time window (0s/5s/15s/30s) + 1 (min: log(2))
 		cell.avgdiffMeter.percent = 1 - (log(CGFloat(src.avg + 1)) / logTimeDelta)
 		return cell
 	}
@@ -86,3 +97,73 @@ class CoOccurrenceCell: UITableViewCell {
 	@IBOutlet var countMeter: MeterBar!
 	@IBOutlet var avgdiffMeter: MeterBar!
 }
+
+
+// MARK: - Tutorial Screen
+
+extension VCCoOccurrence {
+	
+	@IBAction func showInfoScreen() {
+		let sampleCell: UIImage = {
+			let cell = tableView.dequeueReusableCell(withIdentifier: "CoOccurrenceCell") as! CoOccurrenceCell
+			cell.title.text = "example.org"
+			cell.rank.text = "9."
+			cell.count.text = "14"
+			cell.avgdiff.text = String(format: "%.2fs", 0.71)
+			cell.countMeter.percent = 0.35
+			cell.avgdiffMeter.percent = 0.95
+			
+			// Bug: Sometimes dequeue will return a "broken" hidden cell.
+			//      It can't be set visible and thus can't render an image.
+			//      Funnily `cell.contentView` can rendered.
+			let theView = cell.isHidden ? cell.contentView : cell
+			
+			// resize view to fit into tutorial sheet
+			let minWidth = TutorialSheet.verticalWidth - 10 //-> 2 * textContainer.lineFragmentPadding
+			theView.frame.size = theView.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)
+			theView.frame.size.width = min(theView.frame.size.width, minWidth)
+			// set width in two steps because first call may change layoutMargins
+			theView.frame.size.width += theView.layoutMargins.left + theView.layoutMargins.right
+			// FIXME: In case `hidden == false`, backgroundColor will be black in Dark mode.
+			theView.backgroundColor = tableView.backgroundColor
+			return theView.asImage(insets: theView.layoutMargins)
+		}()
+		
+		let x = TutorialSheet()
+		x.addSheet().addArrangedSubview(QuickUI.text(attributed: NSMutableAttributedString()
+			.h3("Co-Occurrence")
+			.normal(" allows you to find requests that happen often at the same time as the selected domain. " +
+					"Hence it will give you a hint what Apps might be involved in the activity." +
+					"\n\nHow do you interpret these results? Lets look at an example:\n\n")
+			.centered(.image(sampleCell))
+			.normal("\n\nThe domain ").bold("example.org").normal(" had ").bold("14").normal(" requests with an ").italic("average time divergence").normal(" of ").bold("0.71 seconds").normal(". " +
+					"That is, these 14 domain calls happend, on average, less then a second before or after the original request of the selected domain." +
+					"\n\nClose temporal proximity and high occurrence counts are both indicators for domain correlation. " +
+					"Results are sorted by a ranking index (").bold("9.").normal(") which strikes a balance between the two. " +
+					"Preferring entries with higher counts as well as low time divergence.")
+			.italic("\n\nTip: ").normal("As a visual guide you can look for the colored bar beside each value. " +
+					"The larger the bar, the greater the correlation.")
+		))
+		
+		x.present(in: self)
+	}
+}
+
+fileprivate extension UIView {
+	func asImage(insets: UIEdgeInsets = .zero) -> UIImage {
+		if #available(iOS 10.0, *) {
+			let renderer = UIGraphicsImageRenderer(bounds: bounds.inset(by: insets))
+			return renderer.image { rendererContext in
+				layer.render(in: rendererContext.cgContext)
+			}
+		} else {
+			UIGraphicsBeginImageContext(bounds.inset(by: insets).size)
+			let ctx = UIGraphicsGetCurrentContext()!
+			ctx.translateBy(x: -insets.left, y: -insets.top)
+			layer.render(in:ctx)
+			let image = UIGraphicsGetImageFromCurrentImageContext()
+			UIGraphicsEndImageContext()
+			return UIImage(cgImage: image!.cgImage!)
+		}
+	}
+}