the app is designed to schedule only 1 alert each time You close the app. this is the default.
it is designed this way, so You have to reopen the app to do the reality test for Your self and close it again. it is trying to force You, to do the test.
the switch Autorepeat Alerts overrides the default behavior by scheduling 64 alerts each time You close the app or leave the Settings.
if You set the Maximum Alert Interval to 30min and set the Autorepeat Alert switch to ON, You would get one alert every 30 minutes.
64 Local Push Notifications is the maximum alerts number that can be scheduled on iOS devices.