Reports the current count of Unavailable Seconds accumulated during the active BERT test, i.e. seconds during which the circuit was considered unavailable due to sustained severe errors. The DESCRIPTION is empty in this MIB, so this reading is inferred from the object name and standard telecom UAS terminology rather than vendor text. A rising UAS count during testing would indicate the circuit dropped into an out-of-service condition for extended stretches, a serious finding for a supposedly working link.