2 players is indeed a little low I think.
Remember: The app will only notify, if the count was below the check-size at one interval AFTER a notificiation.
So if you got a notification, there must be not more than 1 player online over a time of 15 minutes.
Of course, the server is empty, especially in the night and morning (at least in CET).
But following scenario is possible (Checks will met exactly every :00 :15 :30 :45) :
18:00 5 Players -> Notification
19:00 4 Players -> No notification, because already send 18:00
20:00 3 Players -> No notification, because already send 18:00
21:00 2 Players -> No notification, because already send 18:00
enabling airplane mode or shutdown phone
22:00 1 Players -> Won't reset notification, because no connection could be established
23:00 0 Players -> Won't reset notification, because no connection could be established
...
07:00 0 Players -> Won't reset notification, because no connection could be established
...
disabling airplane mode or boot phone
12:00 2 Players -> No notification, because already send 18:00, and there was no reset of notification
13:00 1 Players -> Reset notification
14:00 0 Players -> No notification, because below check-count of 2
...
17:50 2 Players -> No notification, because interval not met
18:00 1 Players -> No notification, because below check-count of 2
18:15 3 Players -> Notification
Of course this is a unlikely scenario, because I don't think that you disabling your airplane mode that late...but nevertheless it is a possible scenario.
But I will check and test it anyway in simulation of Android 10! Because as I said, I found some information, that Android 10 and above has more boot startup restrictions.
Please feel free to give more feedback if another scenario happened.
