This has been suggested many times, and it has been shot down every time.
And sadly the developers don’t plan on adding it.
Luckily i have devised a way for you to keep track of how much profit you have made.
Before or after you sit at the slot machines write down how many units you currently have in the unit counter in the corner.
Then start spinning the machine like you normally would like all the other times you have been in the casino.
Then when you feel like you dont wanna play anymore or gotta go, write down the new number that is in the unit counter.
if the number you wrote down in the start is smaller than the number you wrote down when you were done with the machine, then you have gained profit.
To figure out how much you have earned you just take the current number and use the starting number to subtract from that:
X - Y = Z
X: End units
Y: Starting units
Z: Result
So if you got a starting counter of 207,819 and an end counter of 235,201 then it would go like this:
235201 - 207819 = 27,382 Units Profit