[css-values] Wording tweak

Author: fantasai

css-values/Overview.bs

@@ -693,8 +693,8 @@ Percentages: the <<percentage>> type</h3>
 		where the <<percentage>> will resolve to a <<number>>.
 
 	<div class="example">
-		For example, the 'width' property accepts a <<length>> or a <<percentage>>,
-		where both represent a distance.
+		For example, the 'width' property can accept a <<length>> or a <<percentage>>,
+		both representing a measure of distance.
 		This means that ''width: calc(500px + 50%);'' is allowed--
 		both values are converted to absolute lengths and added.
 		If the containing block is ''1000px'' wide,