[css-ruby] minor disambiguation

Author: frivoal

css-ruby-1/Overview.bs

@@ -868,7 +868,7 @@ Inline-axis Interlinear Layout</h4>
 	Each [=ruby base=] and [=ruby annotation=]
 	is then sized to exactly span its column(s).
 
-	Note: If there are multiple annotations spanning the same number of bases
+	Note: If there are multiple annotations in different levels spanning the same number of bases
 	that overlap but do not coincide,
 	the distribution of space is undefined.
 	Note this is not possible with HTML markup,