A read-only integer, from 1 to 1024, identifying which repeater group within the hub a table row's environmental data belongs to, and never exceeding the hub's total group capacity. Multi-group repeater hubs organize their ports into groups, often corresponding to physical stack units, so this index lets an admin correlate an environmental alarm like high-temp or fan-fail back to the specific group it came from. A value of 3 would indicate the row's data applies to the third repeater group in the hub.