[css-pseudo-4] Wording tweak

Author: fantasai

css-pseudo-4/Overview.bs

@@ -122,7 +122,7 @@ Finding the First Formatted Line</h4>
 
   * The <dfn export>first formatted line</dfn> of
     a [=block container=] that establishes an [=inline formatting context=]
-    contains the [=inline-level=] content of its first [=line box=].
+    represents the [=inline-level=] content of its first [=line box=].
   * The [=first formatted line=] of
     a [=block container=] or [=multi-column container=]
     that contains [=block-level=] content
@@ -140,7 +140,7 @@ Finding the First Formatted Line</h4>
   and will not be affected by ''p::first-line''.
 
   Note: The first line of a [=block container=]
-  that does not participate in a [=block formatting context=]
+  that does not itself participate in a [=block formatting context=]
   cannot be the first formatted line of an ancestor element.
   Thus, in <code class="lang-markup">&lt;DIV&gt;&lt;P STYLE="display: inline-block"&gt;Hello&lt;BR&gt;Goodbye&lt;/P&gt; etcetera&lt;/DIV&gt;</code>
   the first formatted line of the <code>DIV</code> is not the line “Hello”,