Number of station maintenance opportunities to monitor for ranging retry trigger. This value implies time intervals in a certain range. DOCSIS requires the CMTS to schedule ranging opportunity to Cable Modem sufficiently smaller than T4. There is no fixed formula to derive at a fixed time interval, how many ranging opportunities would be offered to a Cable Modem by the CMTS, hence using the number of station maintenance opportunities provides ratio with the fixed denominators while also taking time factor into consideration.