[css-sizing-3][css-align-3] Clarify computed as vs. behaves as auto. w3c#4525

Author: fantasai

css-align-3/Overview.bs

@@ -1283,7 +1283,9 @@ Inline-Axis (or Main-Axis) Alignment: the 'justify-self' property</h3>
 
 		: <dfn>stretch</dfn>
 		::
-			When the box’s computed 'width'/'height' (as appropriate to the axis) is ''width/auto''
+			When the box’s [=computed value|computed=] 'width'/'height'
+			(as appropriate to the axis)
+			is ''width/auto''
 			and neither of its margins (in the appropriate axis) are ''margin/auto'',
 			sets the box’s used size to the length necessary to make its outer size
 			as close to filling the <a>alignment container</a> as possible

css-sizing-3/Overview.bs

@@ -518,9 +518,9 @@ Sizing Values: the <<length-percentage>>, ''width/auto'' | ''max-width/none'', '
 	the property is said to <dfn export lt="behave as auto|behaves as auto|behaving as auto">behave as auto</dfn>
 	in both of these cases.
 
-	Note: Legacy spec prose defining layout behavior
+	Note: Legacy spec prose defining layout behavior, particularly in [[CSS2]],
 	might explicitly refer to 'width'/'height' having a computed value of ''width/auto'' as a condition;
-	these should be interpreted as meaning <a>behaves as auto</a>,
+	some of these cases should be interpreted as meaning <a>behaves as auto</a>,
 	and reported to the CSSWG for updating.
 
 	ISSUE: Replace this section with references to the new term <a>automatic size</a>.