[css-tables] Editorial; fix #1688

Author: FremyCompany

css-tables-3/Overview.bs

@@ -1788,7 +1788,8 @@ spec:css-sizing-3; type:property; text:box-sizing
 					the sum of columns width meets the assignable table width exactly.
 
 				- Columns whose size is computed as a sum of a percentage and a pixel length must be sized as if they counted as two columns,
-					one with the pixel value, the other with the percentage value.
+					one with the pixel value, the other with the percentage value. This is different from resolving the percentage away,
+					because of how width distribution works for percentage-based columns.
 
 
 		<h5 id="distributing-width-to-columns">Distributing excess width to columns</h5>