Port Fowarding multiple ports on Nighthawk MR1100

[Amps]

Greetings, I'm having some trouble port forwarding on my Nighthawk M1, firmware NTG9X50C_12.05.05.00. Is there a way to add multiple ports at a time, or do they need to be input individually?  For example, if I'm trying to input 3478-3480, I type in 3478-3480 but only 3478 shows up in the port fowarding list. Maybe I'm using the wrong syntax?

[Amps]

Bump with more info. I need to port forward ports 7000-8000, how can I do that through the wifi manager?