What is it doing for you?
For me it just will not show "test" after the first post on every thread (page 1,2,3,etc..)
The last condition to to stop it showing in the conversations.
Template ad_message_below
HTML:
<xen:hook name="ad_message_below" />
<xen:if is="{$post.position} == 0 AND !{$visitor.user_id} AND !{$message.conversation_id}">
<Code>
</xen:if>