[css-overflow-3] Tighten up definition of overflow-clip-margin

Author: fantasai

css-overflow-3/Overview.bs

@@ -503,7 +503,7 @@ Scrolling Origin, Direction, and Restriction</h3>
 	The viewport uses the <a>principal writing mode</a> for these calculations.
 
 <h3 id="overflow-clip-margin">
-Expanding ''overflow:clip'' Bounds: the 'overflow-clip-margin' property</h3>
+Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 
 	<pre class=propdef>
 	Name: overflow-clip-margin
@@ -514,17 +514,14 @@ Expanding ''overflow:clip'' Bounds: the 'overflow-clip-margin' property</h3>
 	Computed value: the computed <<length>>
 	</pre>
 
-	Unlike the scrollable 'overflow' values,
-	which have various additional effects on an element
-	to make it a scroll container,
-	''overflow: clip'' solely has the effect
-	of preventing an element from painting outside its bounds.
-	The 'overflow-clip-margin' property
-	determines precisely <em>how far</em> outside its bounds
-	the element is allowed to paint
-	before being clipped.
-
-	The <dfn export>overflow clip edge</dfn> initially coincides with the [=padding edge=],
+	This property defines the <dfn export>overflow clip edge</dfn> of the box,
+	i.e. precisely <em>how far</em> outside its bounds
+	the box’s content is allowed to paint
+	before being clipped
+	by effects (such as ''overflow: clip'')
+	that are defined to clip to the box’s [=overflow clip edge=].
+
+	The [=overflow clip edge=] initially coincides with the [=padding edge=],
 	but can be expanded outwards by 'overflow-clip-margin',
 	as defined below.