[css-cascade] Tweak wording for Specificity (#11445)

Fixes #11305

Author: bramus

css-cascade-6/Overview.bs

@@ -147,9 +147,12 @@ Cascade Sorting Order</h3>
 
 		<dt id='cascade-specificity'>Specificity
 		<dd>
-			The <a href="https://www.w3.org/TR/selectors/#specificity">Selectors module</a> [[!SELECT]] describes how to compute the specificity of a selector.
-			Each declaration has the same specificity as the style rule it appears in.
-			The declaration with the highest specificity wins.
+			The <a href="https://www.w3.org/TR/selectors/#specificity">Selectors module</a> [[!SELECT]]
+			describes how to compute the specificity of a selector.
+
+			When comparing declarations from two style rules,
+			the declaration belonging to
+			the style rule with the highest specificity wins.
 
 		<dt id='cascade-proximity'><dfn>Scope Proximity</dfn>
 		<dd>