[css-grid] Slightly reword the definition of 'available space'.

--HG--
extra : rebase_source : 3055bb4a7d43f6e0bca39e715aae9f064bd3b56b

Author: tabatkins

css-grid/Overview.bs

@@ -3022,11 +3022,11 @@ Definition of Terms for use in Calculating Grid Track Sizes</h3>
 
 		<dt><dfn>remaining space</dfn>
 		<dd>
-			Equal to the <a>available space</a> minus the sum of the <a>base sizes</a> of all the grid tracks.
+			Equal to the <a>available space</a> minus the sum of the <a>base sizes</a> of all the grid tracks
+			or zero,
+			whichever is greater.
 			This value can change over the course of the algorithm,
 			as <a>base sizes</a> are adjusted.
-			If the sum of the <a>base sizes</a> is greater than the <a>available space</a>,
-			the <a>remaining space</a> is instead zero.
 
 			If <a>available space</a> is <a>indefinite</a>,
 			the <a>remaining space</a> is <a>indefinite</a> as well.

css-grid/Overview.html

@@ -2996,11 +2996,11 @@ <h3 class="heading settled heading" data-level=11.1 id=algo-terms><span class=se
 
 		<dt><dfn data-dfn-type=dfn data-noexport="" id=remaining-space>remaining space<a class=self-link href=#remaining-space></a></dfn>
 		<dd>
-			Equal to the <a data-link-type=dfn href=#available-space title="available space">available space</a> minus the sum of the <a data-link-type=dfn href=#base-size title="base sizes">base sizes</a> of all the grid tracks.
+			Equal to the <a data-link-type=dfn href=#available-space title="available space">available space</a> minus the sum of the <a data-link-type=dfn href=#base-size title="base sizes">base sizes</a> of all the grid tracks
+			or zero,
+			whichever is greater.
 			This value can change over the course of the algorithm,
 			as <a data-link-type=dfn href=#base-size title="base sizes">base sizes</a> are adjusted.
-			If the sum of the <a data-link-type=dfn href=#base-size title="base sizes">base sizes</a> is greater than the <a data-link-type=dfn href=#available-space title="available space">available space</a>,
-			the <a data-link-type=dfn href=#remaining-space title="remaining space">remaining space</a> is instead zero.
 
 <p>			If <a data-link-type=dfn href=#available-space title="available space">available space</a> is <a data-link-type=dfn href=http://dev.w3.org/csswg/css-sizing-3/#indefinite title=indefinite>indefinite</a>,
 			the <a data-link-type=dfn href=#remaining-space title="remaining space">remaining space</a> is <a data-link-type=dfn href=http://dev.w3.org/csswg/css-sizing-3/#indefinite title=indefinite>indefinite</a> as well.