[css-ruby] Editorial tweak

Author: frivoal

css-ruby-1/Overview.bs

@@ -1421,8 +1421,10 @@ Sharing Annotation Space: the 'ruby-merge' property</h3>
 			as [=inline boxes=] within their [=annotation container=],
 			and laid out in a single anonymous [=ruby annotation box=]
 			spanning all their associated [=ruby base boxes=].
-			This style renders similar to “group ruby” in [[JLREQ]],
-			except that [=ruby annotations=] are kept together with their respective [=ruby bases=] when breaking lines.
+			When laid out on a single line,
+			this style renders similar to “group ruby” in [[JLREQ]].
+			However, when it breaks across lines,
+			[=ruby annotations=] are kept together with their respective [=ruby bases=].
 
 			<figure>
 				<img src="images/ruby-merge.png"