This read-only Integer32 is the index that identifies which destination (Reflector) a row of ESA probe distribution statistics belongs to, for probes that support point-to-multipoint SLA measurement. An administrator relies on it to know which remote endpoint's performance data a given statistics row describes when a probe is testing multiple destinations at once. The description notes that on Release 4.1 GE206 this value is always 1 because only point-to-point SLA is supported there, so a monitoring script reading this OID on that release would never see any value other than 1.