This is a bitmap (PmProfileFieldMapBasicOdu) that marks which counters within this same profile/row have been declared unsupported on this particular hardware, per the MIB's description, meaning any field flagged here should be disregarded. This bitmap exists because not every line card or ODU variant that shares the 'Basic ODU' PM profile actually implements every counter in it -- so before trusting a zero in, say, the FC or UAS field of this same row, an admin has to check this bitmap first to make sure that field isn't simply unsupported on this hardware rather than genuinely error-free; because this bin is the still-open, currently-accumulating interval, its value is only a partial count until the bin's Duration elapses and it rolls into history -- polling it twice a few minutes apart is the fastest way to catch a fault building up in near real time. If the bit corresponding to FcOdu is set in this bitmap for a given row, an admin comparing failure counts across two different line-card models would know to exclude that field for this one rather than misread its zero as 'no failures.'