esaProbeHistoryLostPkts is a 64-bit performance counter counting, combined across both directions, the test packets never received back from the reflector before timeout, for a completed interval that has already closed and been archived into the rolling history log; it does not apply to Y.1731 probes. This combined figure is the headline number a technician reports against the SLA's packet-loss commitment without manually adding the two directional loss counters together. For example, exporting this total from every archived bin over a billing month lets an operations team calculate the actual monthly loss percentage owed under an SLA credit clause.