Bump certificate, can I use for anything?

Did my OLCI for my trip MEM-DFW, and I got the offer screen. Sure I'm interested.

Quick question... If I get the 400$, can it be used as a credit for ANY ticket??

I am going to Rome in June, and I would like to apply it to that ticket, and pay the difference?

I am not restricted because the original flight was domestic, and what I want to apply it to is International.

Thanks!