Fix description of computing pointer-interactable paint tree

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

Author: yezhizhen

index.html

@@ -4686,13 +4686,13 @@ <h3>Interactability</h3>
  is produced this way:
 
 <ol>
- <li><p>If <var>element</var> is <a>not in the same tree</a>
+ <li><p>If <a><var>element</var></a> is <a>not in the same tree</a>
   as <var>session</var>&apos;s <a>current browsing context</a>&apos;s
   <a>active document</a>, return an empty sequence.
 
  <li><p>Let <var>rectangles</var> be
   the {{DOMRect}} sequence
-  returned by calling {{Element/getClientRects()}}.
+  returned by calling {{Element/getClientRects()}} on <a><var>element</var></a>.
 
  <!--
   An element which style property `display` is "none"
@@ -4702,7 +4702,7 @@ <h3>Interactability</h3>
   return an empty sequence.
 
  <li><p>Let <var>center point</var> be the <a>in-view center point</a>
-  of the first indexed element in <var>rectangles</var>.
+  of <a><var>element</var></a>.
 
  <li><p>Return the <a>elements from point</a>
   given the coordinates <var>center point</var>.