Add sentence to Dirty Flag.

Author: munificent

book/dirty-flag.markdown

@@ -607,7 +607,8 @@ on the ship this modification occurred.
     * *You end up processing unchanged data.* Add a single barrel to a deck
         and you'll have to send the whole thing to the server.
 
-    * *Less memory is used for storing dirty flags.*
+    * *Less memory is used for storing dirty flags.* Add ten barrels to a deck
+        and you only need a single bit to track them all.
 
     * *Less time is spent on fixed overhead.* When processing some changed data,
        there's often a bit of fixed work you have to do on top of handling the

html/dirty-flag.html

@@ -633,7 +633,8 @@ <h3><a href="#how-fine-grained-is-your-dirty-tracking" name="how-fine-grained-is
     and you&#8217;ll have to send the whole thing to the server.</p>
 </li>
 <li>
-<p><em>Less memory is used for storing dirty flags.</em></p>
+<p><em>Less memory is used for storing dirty flags.</em> Add ten barrels to a deck
+    and you only need a single bit to track them all.</p>
 </li>
 <li>
 <p><em>Less time is spent on fixed overhead.</em> When processing some changed data,