This reports how many modules in this DC group are deliberately powered off by an operator, the DC-side equivalent of tsiACGroupNbModMO, used the same way to distinguish planned maintenance actions from actual faults but scoped to a specific battery string's modules. When maintenance is being performed on a specific DC distribution branch or battery string, this lets an admin confirm the number of intentionally-offline modules matches what was planned for that maintenance window. A technician taking a battery string offline for testing would expect this count to rise by exactly the number of modules they manually powered down as part of that procedure.