This field reports the total number of octets transmitted on this PM instance, exposed here as cienaCesPmExtendedTxRxAllTimeBinTxTBytes. On this Ciena CES port's PM data, the description for this field is essentially identical to the sibling TxBytes counter ('total number of octets transmitted' vs 'number of octets transmitted'), so in practice it's Ciena's secondary cumulative-labeled egress byte counter for the same PM instance — the two should track each other closely, and any persistent, growing gap between them on this port is itself worth flagging rather than assuming they're simply redundant; and this 'all-time' counter for the extended Tx/Rx PM group has no fixed rollover schedule of its own — it just keeps accumulating from whenever the PM instance was last cleared, so a single reading only tells you the running total, not a rate. For example, a moderately busy port showing 642,000,000,000 total bytes transmitted for this bin would be a plausible, unremarkable reading.