This counter tracks the number of CLP-0, high-priority, cells received from the PXM port and subsequently discarded for this channel. Because CLP-0 traffic is meant to be protected from loss, any nonzero value here signals a serious problem such as severe congestion or a misconfigured threshold, on a connection that's supposed to be the last to drop cells. An admin seeing bbChanDscdClp0Cells increment on a channel would treat it as a higher-priority troubleshooting item than the equivalent CLP-1 discard counter.