clarify the simultaneous sentence

Author: fantasai

css3-text/Overview.html

@@ -89,7 +89,7 @@ <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 27 April 2011</h2>
     <dt>This version:
 
     <dd><a href="http://dev.w3.org/csswg/css3-text/Overview.html">$Date:
-     2011/04/27 01:29:19 $ (CVS $Revision$)</a> <!--
+     2011/04/27 01:38:57 $ (CVS $Revision$)</a> <!--
       <dd><a href="http://www.w3.org/TR/2011/WD-css3-text-20110427/">http://www.w3.org/TR/2011/WD-css3-text-20110427/</a></dd>
     -->
 
@@ -3729,7 +3729,7 @@ <h4 id=fullwidth-collapsing><span class=secno>9.3.1. </span> Fullwidth
 
   <p>Some fonts use proportional glyphs for fullwidth punctuation characters.
    For such proportional glyphs, the given advance width is considered
-   simultaneously full-width and half-width.
+   simultaneously full-width and half-width: no space is added or removed.
 
   <p class=note>The advance width of a standard Han character can be
    determined either from font metrics such as the OpenType <code>ideo</code>

css3-text/Overview.src.html

@@ -2759,7 +2759,7 @@ <h4 id="fullwidth-collapsing">
 
     <p>Some fonts use proportional glyphs for fullwidth punctuation characters.
       For such proportional glyphs, the given advance width is considered
-      simultaneously full-width and half-width.
+      simultaneously full-width and half-width: no space is added or removed.
 
     <p class="note">The advance width of a standard Han character can be
       determined either from font metrics such as the OpenType <code>ideo</code>