[css-values-5][editorial] Rephrase the calc-size()/non-calc-size() interpolation paragraph for clarity. w3c#10220

Author: tabatkins

css-values-5/Overview.bs

@@ -1883,9 +1883,13 @@ so the ''calc-size()'' has to masquerade as one or the other.
 This, unfortunately, means you can't transition between keywords,
 like going from ''width/auto'' to ''width/min-content''.
 
-As well, a ''calc-size()'' can be interpolated
-with a <<length-percentage>> or an <<intrinsic-size-keyword>>,
-behaving as if the second value were ''calc-size(<var ignore>value</var>)''.
+Some ''calc-size()'' values can also be interpolated
+with a <<length-percentage>> or an <<intrinsic-size-keyword>>.
+To determine whether the values can interpolate
+and what the interpolation behavior is,
+treat the non-''calc-size()'' value
+as ''calc-size( <var ignore>value</var> )''
+and apply the rules above.
 
 <div class=example>
 	For example, ''calc-size()'' allows interpolation to/from ''height: auto'':