[css-grid] Fix axis ambiguity. #2283

Author: fantasai

css-grid-1/Overview.bs

@@ -1240,7 +1240,8 @@ Automatic Minimum Size of Grid Items</h3>
 	also applies an <a>automatic minimum size</a>
 	in the specified axis
 	to <a>grid items</a> whose 'overflow' is ''overflow/visible''
-	and which span at least one <a>track</a> whose <a>min track sizing function</a> is ''grid-template-rows/auto''.
+	and which span at least one <a>track</a> in that axis
+	whose <a>min track sizing function</a> is ''grid-template-rows/auto''.
 
 	The <a>automatic minimum size</a> for a <a>grid item</a> in a given dimension is
 	its <a spec="css-flexbox">specified size</a> if it exists,