docs: improve release numbering rule for minor numbers

Adding first build of year minor number reset to 0.
Signed-off-by: NBoris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

docs/downloads.html.in

@@ -383,7 +383,8 @@
       <dd>incremented by 1 for the first release of the year (the
         Jan 15th release)</dd>
       <dt><code>minor</code></dt>
-      <dd>incremented by 1 for each monthly release from git master</dd>
+      <dd>reset to 0 with every major increment, otherwise incremented by 1
+        for each monthly release from git master</dd>
       <dt><code>micro</code></dt>
       <dd>always 0 for releases from git master, incremented by 1
         for each stable maintenance release</dd>