I don't know DL specifically but from what I see this is the return fare ...for the bit you don't understand ..
ANC DL SLC104.87Y06/ID90 DL ANC104.87Y06/ID90 209.74 END
means in its parts ANC DL SLC104.87Y06/ID90 DL (boardpoint carrier offpoint fare-between-board-and-off-points ticket-category ) and then DL ANC104.87Y06/ID90 209.74 (carrier offpoint fare-between-board-and-off-points ticket-category and total-fare-for-the-full-routing ... note that the boardpoint is assumed to be the previous offpoint if not specified ).

The 31.26XT in the line 1- USD209.74 31.26XT USD241.00ADT is the sum of the extra taxes which are detailed in the line(s) XT 6.26US 6.20ZP 13.80US 5.00AY i.e. 6.26+6.20+13.80+5.00

Perhaps you where not as explicit as you thought you were or company policy is to always issue returns !!