Rephrase the note about the computed value of calc()

Author: tabatkins

css3-values/Overview.html

@@ -1356,8 +1356,8 @@ <h3 id=calc-notation><span class=secno>8.1. </span> Mathematical
    components computed, with all multiplication/division subexpressions
    resolved, and with all addition/subtraction subexpressions resolved where
    both sides are the same type. <span class=note> Thus, the computed value
-   of a calc() expression can be represented as a tuple of a number, a
-   dimension, and a percentage. </span>
+   of a calc() expression can be represented as either a number or a tuple of
+   a dimension and a percentage. </span>
    <!-- http://lists.w3.org/Archives/Public/www-style/2010May/0001.html
 	This has notes on how we should handle things when calc() is extended to 
 	handle unit mult/div. Related to this is <unit>mod<unit>, which can return

css3-values/Overview.src.html

@@ -897,10 +897,8 @@ <h3 id="calc-notation">
 		and with all addition/subtraction subexpressions resolved where both sides are the same type.
 		<span class='note'>
 			Thus, the computed value of a calc() expression can be represented
-			as a tuple of
-			a number,
-			a dimension,
-			and a percentage.
+			as either a number
+			or a tuple of a dimension and a percentage.
 		</span>
 
 	<!-- http://lists.w3.org/Archives/Public/www-style/2010May/0001.html