Video Slots bonus games

Having been stuck in a casino with my in-laws yesterday throwing money away playing slots I started thinking about the programming done for these machines.

I came up with the theory that when you get to the point where you play a bonus game, the machine has already figured out how much the payout for that bonus will be, before you even begin playing.
For example, let’s say one of the bonus games allows you to pick one of three doors and behind each door their will be the bonus points. After you pick the middle door and get your 100 credits, it shows you that behind left door there was 150 credits and behind right door there was 50 credits. So you think you should have picked left door. I think it doesn’t really matter which door you picked since the machine had already figured it was going to give you 100 credits.
If you picked left or right door the machine would have put 100 credits behind them and put the 50 and 150 behind the other two.

This is a basic example but in some more extensive bonus games like punching squares on a grid for matching amounts and getting zapped if you hit an X, does the machine already know what it’s going to give you, lays out the amounts 25, then 50, then 10, then 75, then a zap, and let’s you pick them so you think you doing it randomly? When in actuality it doesn’t matter which one’s you punch, you’ll still get zapped on your 5th pick?

Any cred to this theory?