This Counter64, despite the source description's text referring generically to octets (likely a documentation copy-paste artifact in the original MIB), is named for and counts ATM cells marked CLP0 (high priority) that were discarded at ingress for exceeding this circuit's ATM traffic contract. Because CLP0 cells are supposed to be the protected, higher-priority traffic, any nonzero count here is more concerning than the same count on the CLP1 (low-priority) discard counter, since it means even traffic meant to be preserved is being lost. For example, a nonzero circuitInCLP0CellsDiscard count alongside a much larger circuitInCLP1CellsDiscard count would still be worth flagging, since it indicates the circuit is so overloaded that even protected cells are being sacrificed.