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 specific bin belongs to the completed-interval history table, its value is frozen the moment the interval closes, so re-polling it later will return the same number -- useful for pinpointing exactly which past 15 minutes a problem occurred in. 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.'