Can you explain "Push notification frequency" Doorbell setting better?

breezer

What does the push notification frequency setting actually do? ie. What does it mean when it is set to 20 seconds (the default)? I can't guess it. For further context, I am wondering if it is that it sends a notification every 'setting value' seconds (eg. 20) while a notification event is happening? Is it doing a check-in every 20 seconds when nothing is happening? (would that cause extra network or power usage in the phone for normal non-notification times if I change it to a shorter time?)