This identifies the type of interface module installed in the DIM 2 slot on this board, the second of two detachable interface positions. Since a board can apparently host two independent interface modules, DIM 1 and DIM 2, this lets an admin see the second interface type separately, which matters if the two slots on the same board are wired to serve different port types or connector standards. For example, a board reporting RS-232 for DIM 1 and V.35 for DIM 2 would tell an admin that board can simultaneously serve two different physical interface standards.