This value records the reverse QoS class that had been requested for this failed call, per the description, the return-path counterpart to svcAtmFailedCallAtmQosClass. Because forward and reverse QoS classes can be requested independently on an SVC, this field tells you specifically whether the return-path service class was the source of an admission or negotiation failure, separate from the forward class. A failed call showing a demanding reverse QoS class paired with an ordinary forward class points specifically at return-path service-class provisioning as the likely bottleneck.