This read-only Integer32 identifies which internal Mongoose switch-fabric queue a set of per-queue statistics describes; in the initial phase this number equals the associated VCI, and the description notes that in the 3.0 release there is only a single Ethernet queue, numbered 5. Knowing the queue number lets an admin correctly interpret the accompanying Rx/dropped/CRC counters as belonging to a specific traffic class rather than assuming they're generic. For example, an engineer reviewing per-queue stats on a 3.0-release ComPort would expect stuAtmStuQNo to read 5, confirming the accompanying counters describe the single Ethernet queue rather than some other traffic class.