This identifies a specific VLLI instance group, a set of monitored sources and associated recovery actions grouped together for fault-propagation purposes, by a numeric ID from 1 to 1024, and because it's accessible-for-notify rather than a readable configuration value, it exists primarily to appear as an identifying field within trap notifications about that group. An admin receiving a VLLI-related trap uses this ID to correlate the alert back to the specific group configuration, its direction, trigger mode, and associated recovery actions, defined elsewhere in this table. For example, a trap referencing instance group ID 42 tells the admin exactly which pre-configured fault-propagation group experienced the event, out of potentially over a thousand possible groups on a large device.