How to find out how long the AlarmManager, BroadcastReceiver will be called?

Question

Java

Good afternoon.
I'm making a reverse timer for notifications, I can't figure out how to find out how long the AlarmManager, BroadcastReceiver will be called?
The notification code itself was taken from here:
https://habrahabr.ru/sandbox/34130/
Or tell me in what other way you can restore 1 energy per 1 hour in the game and a reverse report timer for this.
Thank you.