The simple answer to that question is yes, but I dropped the messages because they added clutter to the event log and caused some confusion. Something similar happens when the modem's internal counters pass their maximum values and roll over to zero. In this case I record the new total as the amount of data in that sample (unless it's too high to be believable).
The background to this is that getting the right data from the modem, using the correct interface, has always been a bit hit and miss. This is why I still describe the traffic monitoring as experimental. All I can say is that with correct configuration the reported data seems to be a fairly good representation of the truth.