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 a closed, archived 24-hour interval, admins typically read it the next day to judge whether the previous day as a whole met SLA rather than to catch a fault as it happens. 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.'