This is a running count of packets that have been transmitted out through this specific adjacency. Because an adjacency represents one specific neighbor relationship rather than an entire interface, this counter lets an admin see per-neighbor traffic load even when many adjacencies share the same physical interface, such as on a multi-access LAN segment with several next hops. On a router with three next-hop neighbors sharing one Ethernet interface, this counter can reveal that one particular neighbor's adjacency is carrying the vast majority of traffic while the other two are comparatively idle.