[css-sizing-3] Fix misuse of “outer size” in box-sizing definition. (Thanks for noticing, gsnedders!)

Author: fantasai

css-sizing-3/Overview.bs

@@ -509,7 +509,7 @@ Containing or Excluding Floats</h4>
 -->
 
 <h3 id="box-sizing">
-Inner vs Outer Sizes: the 'box-sizing' property</h3>
+Box Edges for Sizing: the 'box-sizing' property</h3>
 
 
 	<pre class="propdef">
@@ -535,7 +535,8 @@ Inner vs Outer Sizes: the 'box-sizing' property</h3>
 		<dd>
 			Sizes specified on <a>sizing properties</a>
 			as <<length-percentage>>
-			represent <a>inner sizes</a>:
+			represent the box’s <a>inner sizes</a>,
+			excluding the margins/border/padding:
 			they are applied to the <a>content box</a>.
 			The padding and border of the box
 			are laid out and drawn <em>outside</em> the specified 'width' and 'height'.
@@ -547,7 +548,8 @@ Inner vs Outer Sizes: the 'box-sizing' property</h3>
 		<dd>
 			Sizes specified on <a>sizing properties</a>
 			as <<length-percentage>>
-			represent <a>outer sizes</a>:
+			represent the box’s visually-apparent sizes,
+			including the borders/padding (but not margin):
 			they are applied to the <a>border box</a>.
 			The padding and border of the box
 			are laid out and drawn <em>inside</em> the specified 'width' and 'height',
@@ -574,8 +576,9 @@ Inner vs Outer Sizes: the 'box-sizing' property</h3>
 	(unless otherwise specified).
 
 	<div class=example>
-		For example, the following properties set the <a>inner size</a> of the box to ''100px'',
-		and the <a>outer size</a> to ''120px'':
+		For example, the following properties set
+		the content-box size of the box to ''100px'',
+		with the border-box size calculating to ''120px'':
 
 		<pre class=lang-css>
 		.box {
@@ -587,8 +590,8 @@ Inner vs Outer Sizes: the 'box-sizing' property</h3>
 		</pre>
 
 		On the other hand, by changing to ''border-box'',
-		the <a>inner size</a> is now ''80px'',
-		while the <a>outer size</a> is ''100px'':
+		the border-box is set to ''100px'',
+		with the content-box size calculating to ''80px'':
 
 		<pre class=lang-css>
 		.box {
@@ -600,11 +603,11 @@ Inner vs Outer Sizes: the 'box-sizing' property</h3>
 		</pre>
 
 		The <a>inner size</a> can't be less than zero,
-		so if the 'padding' + 'border' is greater than the specified <a>outer size</a>,
+		so if the 'padding' + 'border' is greater than the specified border-box size,
 		the box will end up larger than specified.
-		In this case, the <a>inner size</a> will be ''0px''
-		while the <a>outer size</a> is ''120px'',
-		even though ''width: 100px'' is specified:
+		In this case, the content-box size will floor at ''0px''
+		so the border-box size ends up at ''120px'',
+		even though ''width: 100px'' is specified for the border box:
 
 		<pre class=lang-css>
 		.box {