This read-only PerfCounter64 reports the sum of squares of forward (P2R) Frame Delay Range samples, in microseconds squared, collected during the current interval, per its description. An administrator's analysis tools use this with the sum and count to compute the variance or standard deviation of forward-path delay variation, revealing consistency rather than just a single average. For example, an engineering team benchmarking path stability would use f3EsaProbeStatsSoamPmExtSumOfSqP2RFDR to compute standard deviation and compare it against a target consistency threshold.