To be honest it was a typo.
We already has the zone in our database.
Code:
<ImageStyle Name="adv02_dun_sundered_playground_0" displayname="Sundered Splitpaw: Upper Tunnels" zonerect="-111, -265, 150, 33" heightmin="-51">
<ImageFrame Source="images/maps/map_adv02_dun_sundered_splitpaw_1.dds" SourceRect="0,0,436,506" />
</ImageStyle>
But now im not sure what the name should be, as you got the name: adv02_dun_sundered_splitpaw_playground
But the thing i wanted to change was to remove "heightmin" as im not sure why its there.
More testing is needed.