This Counter64 counts severely errored seconds for this pseudowire — seconds during the cumulative bin whose error rate was high enough to cross the severely-errored threshold at the PW/service layer. Because this is the cumulative TdmPwTotalStatistics counter for the pseudowire, tallied since the bin's own start time rather than being reset every short collection interval, Ses is a stricter, higher-severity version of Es, and per standard TDM performance definitions accumulating enough consecutive severely errored seconds is what eventually triggers an Uas (unavailable seconds) count. For example, ten consecutive Ses increments in the same short span is the classic trigger pattern that would also start incrementing this pseudowire's Uas counter.