Consumer connections from STOMP clients that use composite destinations ("dest1,dest2") are represented in JMX differently from JMS clients. The representation seems to be appropriate for a single consumer ,rather than a composite. At least some of the values seems to be incorrect.
For example, the "enqueue count" and "dequeue count" values never change, regardless of the number of messages passed. The "consumer count" value is always one below the actual number of consumers (so if no consumers are connected, it shows -1). I suspect that some of the other values are also wrong, but it's harder to test them definitively.