Perhaps what you need to override is ZO_NotificationList:FilterScrollList()
edit: no, that wouldn't report correct numbers. So post-hook ZO_LeaderboardRaidProvider:BuildNotificationList(), removing undesired entries (which is all of them? if so, no need to call original, just ZO_ClearNumericallyIndexedTable(self.list) and done
)
edit2: lol, exactly Garkin, I just edited it before reading your post
