This read-only PerfCounter64 is the historical counterpart to f3EsaProbeStatsSoamPmExtMaxR2PFDR, recording the worst backward (R2P) Frame Delay Range spike observed during a completed, archived interval. An administrator checks this when a past return-path delay complaint needs a concrete archived figure to confirm. For example, an operator would pull f3EsaProbeHistorySoamPmExtMaxR2PFDR for the disputed interval to see if the return path had an unusual delay spike at that time.