[css-values] Clarify short-circuiting behavior in an example closer to the prose that causes it (pulled from shorthand example).

Author: fantasai

css-values/Overview.bs

@@ -1689,6 +1689,12 @@ Toggling Between Values: ''toggle()''</h3>
 	or there was no match,
 	the computed value of ''toggle()'' is the computed value that the first argument represents.
 
+
+	Note: This means that repeating values in a ''toggle()'' short-circuits the list.
+	For example ''toggle(1em, 2em, 1em, 4em)'' will be equivalent to ''toggle(1em, 2em)''.
+
+	<!-- Issue: Should this short-circuiting affect the computed value? -->
+
 	Note: That ''toggle()'' explicitly looks at the computed value of the parent,
 	so it works even on non-inherited properties.
 	This is similar to the ''inherit'' keyword,
@@ -1736,6 +1742,8 @@ Toggling Between Values: ''toggle()''</h3>
 		margin-bottom: toggle(1px, 3px);
 		margin-left:   toggle(2px, 4px, 5px);
 		</pre>
+
+		which may not be what was intended.
 	</div>
 
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