This field is a bitmask, preserved in this archived FCoE interface history record, showing which configured alarm thresholds the monitored values had crossed at the moment this particular snapshot was taken. Because it's frozen into the historical record rather than the live object, admins can use it to reconstruct exactly when a FCoE interface counter first crossed its threshold, even after the live value has since dropped back under the limit. For example, scanning back through this interface's history records for the first one where this bitmask turned nonzero would pinpoint the exact collection interval an alarm condition began.