All of my info is plugged in so when I book a ticket, I don't touch a thing, but glitches in the system happen - it may not be your fault. One time, the system displayed my name on the ticket as "first name, first name" and it was corrected with a phone call with no pushback. Recently I booked a ticket and it displayed my name as "first namemr, last name" and after a phone call told it was correct in their system even though it was not displaying correctly for me. Should be an easy fix if on DL metal, and it might be a challenge if there are codeshares (see DLMiddleSeats comment), but agents will do their best to fix it - being nice and polite on the phone really helps. I would not panic at this stage.