As the description states, this is a bitmap mapping which fields within this PM profile have been declared unsupported on this card or module; any field flagged here in the same table row should simply be disregarded. On a transponder that doesn't expose Pre-FEC BER granularity, this bitmap on a History row would flag the PrfBerOtu/PrfBerMaxOtu bits so a monitoring tool skips them instead of graphing a meaningless zero and mistaking it for a real reading. For example, a nonzero bit pattern here paired with a flat 0 reading on one of those flagged fields in the same row tells you the zero means 'not measured', not 'nothing detected'.