DM card is UA speak for seat request. I am fortunate/cursed to work both Delta and United systems. SkyWest in GJT has 8 UA flights to DEN and 4 DL flights to SLC. The learning curve is double or maybe even triple (for old guys). Some days we bounce back and forth between working either carrier.
The UA system lets us checkin for NRSA travel and print DM cards/seat request 24 hours prior to flight time. The Delta system gives a much better picture of the non-rev list, where WebList only shows the total number of NRSAs listed.
While on this digression...the UA voice driven listing system actually works fairly well in the noisy environment of a jet taxing to the gate or a crowded concourse. If there is trouble you get transferred to a friendly to a human.