Port forwarding on Airport Extreme?

Hello, hope some kind person can help clear this up for me

I seem to be able to search, upload and download fine but everytime I try the check the ports I'm forwarding I get the message that it's CLOSED.

I've followed so many guides but still can't get this right.

First of all, do I actually need to do this? Most guides seem to say that Mac does this automatically. I do have NAT Port Mapping Protocol on.

Which ports do I need to have open?

As it stands now I've created a Port caalled "SoulseekQT" type IPv4

Public UDP Ports #####
Public TCP Ports #####
Private IP address XXXXX
Private UDP Ports #####
Private TCP Ports #####

And ##### is the same as in the Soulseek QT client
Should I maybe use one of the preset in the "Description" drop menu?

What am I not understanding right?

Cheers
//Daniel