[2797] add a note for the counters related to EDNS versions

src/bin/auth/b10-auth.xml.pre

@@ -20,7 +20,7 @@
 <refentry>
 
   <refentryinfo>
-    <date>May 22, 2013</date>
+    <date>July 16, 2013</date>
   </refentryinfo>
 
   <refmeta>
@@ -260,6 +260,15 @@
 	of particular interest to have a specific counters for such
 	requests.
       </para>
+
+      <para>
+	There are two request counters related to EDNS:
+	<quote>request.edns0</quote> and <quote>request.badednsver</quote>.
+	The latter is a counter of requests with unsupported EDNS version:
+	other than version 0 in the current implementation. Therefore, total
+	number of requests with EDNS is a sum of <quote>request.edns0</quote>
+	and <quote>request.badednsver</quote>.
+      </para>
     </note>
 
   </refsect1>