This field reports collection start time of the bin, exposed here as cienaCesPmExtendedTxRxTotalStatsBinStartTime. On this Ciena CES port's PM data, this DisplayString timestamp marks exactly when the bin began accumulating, which you need in order to correctly turn any cumulative counter in the same bin into a rate rather than treating it as a mystery running total; and this is the running grand-total counter for the extended Tx/Rx PM group, tallied since the bin's own StartTime (in practice since the PM instance was created or last reset), so treat it as a lifetime tally rather than a per-interval number. For example, this field holding a value like '2026-08-06,14:30:00.0' tells you precisely which wall-clock window the rest of this bin's counters cover.