This is a Counter64 preserving the total notification payloads sent by a now-expired control tunnel over its entire lifetime, per its description, the historical companion to the live cisgIpsSgTunOutNotifys. It shows how many status/error notifications this device itself generated toward a since-closed peer over that connection's life, which if unusually high suggests this device's own handling of that tunnel repeatedly triggered notification events. A history entry showing a high OutNotifys count for a tunnel this device itself terminated (per HistTermReason showing 'operRequest') would be consistent with an admin actively managing a problematic connection before finally closing it.