Opening a range of ports - 20:22

Let me start off by saying that I'm completely new to the Astaro game. So I will go ahead and thank you all for your patience.

I have a Astaro Security Gateway V8 that I'm working with at a client's site. They are trying to connect to an external FTP server using ports between 20:22. and for the life of me I cannot figure out how to get the NAT and Firewall to open that port to any local IP address.

What i have tried is set a DNAT rule with
Traffic Source: External(WAN) (Network)
Traffic Service: FTP 20:22
Traffic Destination: Internal (Network)
NAT Mode: DNAT
Destination: Internal (Address)

With the Auto Firewall rule selected and I'm having no luck. If anyone can get me going in the right direction I would greatly appreciate it!