diff --git a/master/propidx.html b/master/propidx.html
index f42ee355..ca46eb6d 100644
--- a/master/propidx.html
+++ b/master/propidx.html
@@ -261,7 +261,7 @@ <h1>Property Index</h1>
           <td>none</td>
           <td><a>shapes</a> and <a>text content elements</a></td>
           <td>yes</td>
-          <td>N/A</td>
+          <td>refer to the normalized diagonal of the current SVG viewport</td>
           <td><a href="https://www.w3.org/TR/2008/REC-CSS2-20080411/media.html#visual-media-group">visual</a></td>
           <td>See prose</td>
           <td>as comma separated list of absolute lengths or percentages, numbers converted to absolute lengths first, or keyword specified</td>