This is the number of times an adjacency state change has occurred on this circuit. It tallies every up, down, or initializing transition an adjacency on this circuit has gone through, making it the single best per-circuit indicator of link or neighbor instability, since a high count correlates directly with repeated SPF recomputations and LSP churn across the whole area. For example, a circuit showing 40 adjacency changes over a single day, compared to a neighboring stable circuit showing 0, immediately isolates which specific link is responsible for the area's recent instability.