This is a 64-bit counter of multicast bytes (octet count) injected by the router's own higher-layer stack down onto the ring, labeled by its real description simply as the 'total' count rather than explicitly 'low priority' (even though the object's own name says LowPri), measured over one specific, already-completed 15-minute bucket from the rolling 24-hour history, rather than a live count. Because this is measured on the host side, it reflects only traffic this specific router is locally sourcing or sinking, so comparing it against the Ring-side counters on the same box shows how much of what crosses the ring this node actually originates versus just passes through, because SRP always drains high-priority traffic first, a plateau or drop in this low-priority counter while the matching high-priority counter is climbing indicates best-effort traffic is being squeezed out by real-time/control traffic rather than genuinely dropping off, and because multicast frames on a shared ring get passed along until they're stripped off or time out, a sudden multicast surge here more often reflects a flooding condition (e.g. an ARP-like storm or a new multicast subscriber group) than ordinary point-to-point application growth, and pairing this byte count with the matching packet counter for the same traffic class is how you'd derive the average frame size and the actual bit rate that class is consuming. For instance, this counter might read roughly 141,145,600 bytes of multicast traffic over that window, which combined with the matching packet counter lets you compute an average frame size for that class.