This read-only PerfTotalCount reports the count of frames discarded because of receiver overruns on the DSL port, scoped to the DSL port's current, still-accumulating measurement period (not yet rolled into the interval history). Operationally, overruns mean the receive buffer filled up faster than frames could be processed, causing outright data loss. For example, watching this counter during a live load test tells an admin whether the receiver is currently overrunning under the traffic being generated right now.