[css-grid] Clarify that the transferred size has its input clamped just like the automatic minimum size does.

Author: tabatkins

css-grid/Overview.bs

@@ -34,6 +34,10 @@ At Risk: application of grid placement to absolutely-positioned boxes
 
 <pre class="link-defaults">
 spec:css-break-3; type:dfn; text:fragment
+spec: css-flexbox-1; type:dfn
+	text: specified size
+	text: content size
+	text: transferred size
 </pre>
 
 <style type="text/css">
@@ -1251,11 +1255,14 @@ Implied Minimum Size of Grid Items</h3>
 	(The effect is analogous to the <a>automatic minimum size</a>
 	imposed on <a>flex items</a>.)
 	[[!CSS-FLEXBOX-1]]
+
 	However, if the <a>grid item</a> spans only <a>grid tracks</a>
 	that have a <a lt="fixed sizing function">fixed</a> <a>max track sizing function</a>,
-	its <a>automatic minimum size</a> in that dimension
-	is further clamped to less than or equal to the size necessary
-	to fit its margin box within the resulting <a>grid area</a> (flooring at zero).
+	its <a>specified size</a> and <a>content size</a> in that dimension
+	(and the input to the <a>transferred size</a> in the other dimension)
+	are further clamped to less than or equal to the size necessary
+	to fit its margin box within the resulting <a>grid area</a> (flooring at zero),
+	so as to prevent the <a>automatic minimum size</a> from forcing overflow of its fixed-size grid area.
 
 	<div class="note" id="min-size-opt">
 		Note that while a content-based minimum size is often appropriate,