Are you sure those are really gates and not apron parking positions? The remote positions are prefixed VICTOR (with OS flights to GRZ or VIE usually standing on V24 or V25), as you can see here:
http://www.edll-fir.de/fileadmin/use...DL_Parking.pdf.
Flights departing from one of the remote positions will usually be assigned Gate A81 or A83 (the ground level bus gates in concourse A), don't know about the bus gate numbers in other concourses. Upon arrival, there is only a single bus gate (on the other side of the terminal) per concourse, flights arriving there will be assigned a gate number in the lower 90s. There is no D concourse that I knew of.