Clarify how range positions are determined with sticky offsets.

Fixes w3c#8298

Author: flackr

scroll-animations-1/Overview.bs

@@ -413,10 +413,10 @@ spec: cssom-view-1; type: dfn;
 		<dt><dfn>cover</dfn>
 		<dd>
 			Represents the full range of the [=view progress timeline=]:
-			* 0% progress represents the position at which
+			* 0% progress represents the latest position at which
 				the [=start=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=end=] edge of its [=view progress visibility range=].
-			* 100% progress represents the position at which
+			* 100% progress represents the earliest position at which
 				the [=end=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=start=] edge of its [=view progress visibility range=].
 
@@ -425,12 +425,12 @@ spec: cssom-view-1; type: dfn;
 			Represents the range during which the [=principal box=]
 			is either fully contained by, or fully covers,
 			its [=view progress visibility range=] within the [=scrollport=].
-			* 0% progress represents the earlier position at which:
+			* 0% progress represents the earliest position at which either:
 				* the [=start=] [=border edge=] of the element’s [=principal box=]
 					coincides with the [=start=] edge of its [=view progress visibility range=].
 				* the [=end=] [=border edge=] of the element’s [=principal box=]
 					coincides with the [=end=] edge of its [=view progress visibility range=].
-			* 100% progress represents the later position at which:
+			* 100% progress represents the latest position at which either:
 				* the [=start=] [=border edge=] of the element’s [=principal box=]
 					coincides with the [=start=] edge of its [=view progress visibility range=].
 				* the [=end=] [=border edge=] of the element’s [=principal box=]
@@ -454,21 +454,21 @@ spec: cssom-view-1; type: dfn;
 		<dd>
 			Represents the range during which the [=principal box=] crosses the [=end=]
 			[=border edge=]
-			* 0% progress represents the position at which
+			* 0% progress represents the latest position at which
 				the [=start=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=end=] edge of its [=view progress visibility range=].
-			* 100% progress represents the position at which
+			* 100% progress represents the earliest position at which
 				the [=end=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=end=] edge of its [=view progress visibility range=].
 
 		<dt><dfn>exit-crossing</dfn>
 		<dd>
 			Represents the range during which the [=principal box=] crosses the [=start=]
 			[=border edge=]
-			* 0% progress represents the position at which
+			* 0% progress represents the latest position at which
 				the [=start=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=start=] edge of its [=view progress visibility range=].
-			* 100% progress represents the position at which
+			* 100% progress represents the earliest position at which
 				the [=end=] [=border edge=] of the element’s [=principal box=]
 				coincides with the [=start=] edge of its [=view progress visibility range=].
 	</dl>
@@ -480,11 +480,11 @@ spec: cssom-view-1; type: dfn;
 	<a href="http://www.w3.org/TR/css-transforms/">Transforms</a> are ignored,
 	but [=relative positioning|relative=] and [=absolute positioning|absolute=] positioning
 	are accounted for.
-	For [=sticky-positioned boxes=],
-	the box’s [=startmost=] offset position
-	is used when identifying 0% progress,
-	and the box’s [=endmost=] offset position
-	is used when identifying 100% progress.
+
+	Note: For [=sticky-positioned boxes=] a given constraint may be satisfied over
+	a range of scroll positions. Each of the ranges clarifies whether to use the earliest
+	or latest position.
+
 	[[CSS-POSITION-3]] [[CSS-TRANSFORMS-1]]
 
 ## Calculating Progress for a View Progress Timeline ## {#view-timeline-progress}