This counts high-priority CLP0 cells, cells marked as protected from loss, that were nonetheless discarded on this VC, which is significant because CLP0 cells are supposed to be the ones the network protects most under congestion, so any nonzero count here represents a more serious quality problem than losing CLP1 cells. An admin seeing this counter increment at all on a properly-contracted circuit should treat it as a red flag worth escalating, since it implies the switch is under enough stress to be dropping traffic it's contracted to protect. For example, a nonzero cktAtmInDiscardedClp0Cells count on a CBR voice circuit would likely correspond to audible degradation the customer has already noticed, since this traffic class isn't supposed to be dropped under normal conditions.