This read-only PerfCounter64 is the historical counterpart to f3EsaProbeStatsSoamPmExtR2PSeverelyErroredDeltaTs, recording, for a completed archived interval, how many delta_ts had reflector-to-probe FLR exceeding the availability threshold. An administrator compares this archived return-path count against the historical P2R count to see whether past problems were one-directional or bidirectional. For example, an operator reviewing a resolved incident would check whether both historical severely-errored counts spiked together, pointing to a shared-link cause rather than a one-way fault.