This PerfCounter64 counts Errored Seconds encountered by a SONET/SDH VT (virtual tributary) Path in the current bin. Since a VT path typically carries a single low-speed circuit (like a DS1) multiplexed inside a larger STS payload, an admin watches its ES count to isolate a problem to one specific tributary rather than the whole STS frame. If vtVcPathStatsESs climbs on only one of several VT1.5 tributaries riding the same STS-1, the admin knows the fault is specific to that individual customer circuit, not the shared SONET path.