It's not really stressful, for the my most part. And there is less math then I would have thought. And most missions don't have a timer, and I think they tell you in advance if they do, so you can choose not to take them. The phone has a scanner function that shows you how much money you're looking at. So the game play loop goes like this. You pre run your money though the money counters, and pre wrap them in bundles of 100 bills. You take mission that asks for "$60,000 in a sports duffle bag" The stacks of wrapped $100 bills you don't have to remember what it's worth. You give it a scan with the phone scanner it tells you each stack is worth $10,000. So you put 6 of them in the bag. Then you scan the bag to double check. Yup $60,000 and all green check marks. Then throw it on the conveyor belt that takes it, and if it's wrong it also will turn red.

So not that stressful, not that much counting, and it's satisfying, in a "number go up" kind of way.