diff --git a/manpages/shorewall-tcrules.xml b/manpages/shorewall-tcrules.xml
index bf2b103b3..a4bdf26eb 100644
--- a/manpages/shorewall-tcrules.xml
+++ b/manpages/shorewall-tcrules.xml
@@ -141,6 +141,15 @@
               the <emphasis role="bold">SOURCE</emphasis> is <emphasis
               role="bold">$FW</emphasis>[:<emphasis>address</emphasis>] in
               which case marking occurs in the OUTPUT chain.</para>
+
+              <para>When using Shorewall's built-in traffic tool, the
+              <emphasis>major</emphasis> class is the device number (the first
+              device in shorewall-tcdevices(5) is major class 1, the second
+              device is major class 2, and so on) and the
+              <emphasis>minor</emphasis> class is the class's MARK value in
+              shorewall-tcclasses(5) preceded by the number 1 (MARK 1
+              corresponds to minor class 11, MARK 5 corresponds to minor class
+              15, MARK 22 corresponds to minor class 122, etc.). </para>
             </listitem>
 
             <listitem>