This counts high-priority, loss-protected cells the switch has transmitted outbound on this VC, giving the admin the delivered-traffic side of the CLP0 ledger to pair with the inbound pass and discard counters when auditing how well this circuit's protected traffic class is being carried end to end. For example, comparing cktAtmInPassedClp0Cells against cktAtmOutClp0Cells over the same interval should show them tracking closely if the network path is healthy, since almost none of this class should be lost in transit.