This counter tracks the number of RESTART messages, which reset the signaling state of one or all SVCs on this port, clearing any calls that may be stuck or out of sync that this port has transmitted, per the description. This is one of the more disruptive PDUs in Q.93b since it can forcibly clear multiple active calls at once, so this counter should normally be at or near zero, and any nonzero value is worth investigating as a recovery event rather than routine traffic. For example, a jump in this counter to even a handful of RESTARTs in a day would be notable on a stable trunk and worth correlating with any card resets or link outages logged around the same time.