This reports how many modules in this AC group have been deliberately powered off by an operator, the group-scoped equivalent of tsiPhaseNbModMO, used the same way to distinguish planned maintenance from actual faults but scoped to a specific battery feed grouping rather than phase. When maintenance is being performed circuit-by-circuit rather than phase-by-phase, this lets an admin confirm the modules taken offline for a specific circuit's maintenance match the expected count for that group. A technician servicing a specific AC group's shared breaker would expect this count to match however many modules they intentionally powered down before starting work.