[css-overflow-3] Export terms

Author: fantasai

css-sizing-3/Overview.bs

@@ -365,11 +365,11 @@ Sizing Values: the <<length-percentage>>, ''width/auto'' | ''max-width/none'', '
 
 		<dt><dfn for="width, height, min-width, min-height">auto</dfn>
 		<dd>
-			For 'width'/'height', specifies an <dfn dfn for>automatic size</dfn>.
+			For 'width'/'height', specifies an <dfn export dfn for>automatic size</dfn>.
 			See the relevant layout module for how to calculate this.
 
 			For 'min-width'/'min-height',
-			specifies an <dfn dfn for>automatic minimum size</dfn>.
+			specifies an <dfn export dfn for>automatic minimum size</dfn>.
 			Unless otherwise defined by the relevant layout module,
 			however,
 			it resolves to a used value of ''0''.