There isn't an existing template. When a template isn't specified it loads a hardcoded default string. If you want to modify the template then you need to create it as indicated above. It uses the same tokens as you would find in the Active Forums postinfo template.
Go look at your postinfo template in Active Forums. Then go to your profile template and change the tag from
<af:userstats userid="[DNN:PROFILE:USERID]" runat="server" />
to something like this...
<af:userstats userid="[DNN:PROFILE:USERID]" runat="server" >
<template>
<span class="aslabelsmbold">Posts:</span> [AF:PROFILE:POSTCOUNT]<br>
<span class="aslabelsmbold">Rank:</span> [AF:PROFILE:RANKNAME]<br>
<span class="aslabelsmbold">Level:</span> [AF:PROFILE:RANKDISPLAY] <br>
<span class="aslabelsmbold">Last Activity:</span> [AF:PROFILE:DATELASTACTIVITY:d] <br>
<span class="aslabelsmbold">Member Since:</span> [AF:PROFILE:DATECREATED:d]
</template>
</af:userstats>