This field reports the number of received bytes dropped on this PM instance, exposed here as cienaCesPmBasicTxRxHistoryBinRxDroppedBytes. On this Ciena CES port's PM data, this is ingress traffic on this port that was policed and discarded outright rather than merely remarked, so a rising count here (as opposed to RxYellowBytes) means this port's committed+excess bandwidth profile is being violated, not just brushed up against; and this lives in the basic bandwidth-profile-aware PM group's history bin — a closed-out interval whose own Duration and State tell you how long it ran and whether it closed cleanly, so the number is settled rather than still being written to. For example, a healthy port would sit at 0 for dropped bytes in this bin; even 13 is enough to warrant a look, since this class of counter isn't supposed to move under normal operation.