This field reports the number of single collision packets transmitted on the interface, exposed here as cienaCesPmExtendedTxRxAllTimeBinTxSingleCollPkts. On this Ciena CES port's PM data, a single collision followed by a successful retransmit is routine background noise on a shared or half-duplex segment, so this counter climbing steadily (without TxExCollPkts or TxLateCollPkts climbing alongside it) is generally benign; 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 link under light load might show a low but steady 180 single-collision frames for this bin; it's the rate of growth, not the presence of a nonzero number, that would flag a real problem.