They aren't timed returns. It's more general than that as its just a group and they are called in order. They estimate the time the group will be called but that is it. Here is a post in another thread with an example
Guess I didn't realize that you wouldn't be given a specific time for your "boarding group" but just a range and that you would then be notified when to to come ... impacts what you would look to do while waiting
another tweet of screen shots and the third image shows what it looks like after you join a boarding group:
I don’t think it has times. Disneyland daily reports she booked on at 820 and got boarding pass 2.. 20 minutes later they were on 9. I think you just get a notification when it’s your groups time and have 2 hours to use it.