Where Did the Dollar Come From ? Puzzle

The Puzzle:

Where Did the Dollar Come From ?
Two friends have a nice meal together, and the bill is $25

The friends pay $15 each, which the Waiter gives to the Cashier

The Cashier hands back $5 to the Waiter

The Waiter keeps $3 as a tip and hands back $1 each

So, the friends paid $14 each for the meal, for a total of $28. The Waiter has $3, and that makes $31. Where did the other dollar come from?
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