[css-contain] content-visibility affects contain at used value time

This is a follow up on w3c#6246, the prior edit was incomplete.

Author: frivoal

css-contain-2/Overview.bs

@@ -1418,7 +1418,8 @@ Suppressing An Element's Contents Entirely: the 'content-visibility' property {#
 
 		: <dfn>auto</dfn>
 		::
-			Turns on [=layout containment=],
+			Changes the [=used value=] of the 'contain' property
+			so as to turn on [=layout containment=],
 			[=style containment=],
 			and [=paint containment=] for the element.
 
@@ -2069,6 +2070,7 @@ Changes from <a href="https://www.w3.org/TR/2022/WD-css-contain-2-20220917/">202
 </h3>
 
 * 'content-visibility' applies to the same properties as [=size containment=] rather than [=layout containment=]
+* clarified that 'content-visibility' affects the used value, not computed value, of the 'contain' property
 
 <h3 id="changes-since-2020-12-16">
 Changes from <a href="https://www.w3.org/TR/2020/WD-css-contain-2-20201216/">2020-12-16 Working Draft</a>