I've programmed DIDs with a T1 before i.e. line 145 to ext 221, line 146 to ext 222, etc. with received digits but I'm having some issues with a customer that has a 4-channel DID circuit.

My DID lines are 13, 14, 15, and 16. Do I still utilize target lines that are higher then that i.e. line 75, 76, etc. or do I assign these lines (13-16) to specific phones?

The customer has 16 DIDs so do I assign each line to 4 phones to spread it out?

I know my way through the progamming but I'm having some issues with this. Thank you for any assistance you might be able to provide.