It's actually not necessary to port forward that entire range to your ATA, it would work but is overkill. If you need port forwarding at all due to one way audio (not everyone needs to do this), normally you would just port forward the RTP port range defined on your ATA. On my SPA2102 the default range is 16384 to 16482, you would setup a UDP port forward rule to your local ATA IP. In my case I changed this range to something different that didn't conflict with any other programs I use (i.e, 17000 to 1709 and forwarded just that range. If you forward 5004-65000 then it could interfere with other programs that might also need port forwarding, for example Plex Server which uses port 32400.

It is slightly better than using the DMZ which would forward everything to your ATA, but if you want to limit which traffic goes to the ATA it is better to just use the RTP port range. In my case I didn't have to port forward the SIP ports, but if you do that would normally be 5060 (and 5061 if you have 2 lines).

Of course if everything is working fine and you don't get any random calls on your ATA then you could leave everything alone and not worry about it.