[css-scroll-snap] Clarify that scroll-as-far-as-possible is a snapped position, not just an ending position.

Author: fantasai

css-scroll-snap/Overview.bs

@@ -806,6 +806,8 @@ Choosing Snap Positions {#choosing}
 		past the edge of its <a>scrollable area</a>,
 		the <a>scroll container</a> must be scrolled <em>as much as possible</em> in each relevant axis
 		toward the desired <a>snap position</a>.
+		This is the <em>used</em> <a>snap position</a> corresponding to that <a>snap position</a>;
+		that is, the UA must “snap” to this position just as it would have if it were the actual specified alignment.
 
 	* A user agent <em>may</em> want to ignore ''mandatory'' <a>snap positions</a>
 		that are sufficiently far away from the scroll's end point,