[css-multicol] Update overflow section

Fixes: #12632

Author: rachelandrew

css-multicol-2/Overview.bs

@@ -2043,17 +2043,19 @@ Pagination and Overflow Outside Multicol Containers</h3>
 
 	<ul>
 		<li>
-			a declaration that constrains the column height
+			a declaration that constrains the multicol container height
 			(e.g., using 'height' or 'max-height').
-			In this case, additional column boxes are created in the inline direction
+			In this case, additional column boxes are created in the wrapping direction 
+			(by default, the inline direction).
 		</li>
 		<li>
 			the size of the page.
 			In this case, additional column boxes are moved to the next page(s).
 		</li>
 		<li>
 			explicit column breaks.
-			In this case, additional column boxes are created in the inline direction for continuous contexts
+			In this case, additional column boxes are created in the in the wrapping direction 
+			(by default, the inline direction for continuous contexts).
 			and additional column boxes are moved to the next fragment(s) for fragmented media.
 		<li>
 	</ul>