cant make a port forward because your system has the wrong IP

So i have a computer i want to make a port forward to.

i set it a reserved IP which is working fine.. but when i go into the XFi thing and do the port forward when i select the comptuer from the list it shows the wrong IP.

the IP im using is 192.168.1.50 and the IP your system thinks the PC has is 192.168.1.22

WHY CANT I CHANGE THE IP MANUALLY?? this seems like a basic feature that is removed. 😞