Do you guys play logicals?

Like I went to a restaurant lately for lunch with two colleagues... each of us had a bill of 10€, but when we had payed the waitress, the owner told her that she should only charge und three 25€, as we go there regularly... which put her in despair, as she didn't know how to split up the 5€ among us three... she decided to give each of us a Euro back, and just keep the remaining 2€ as an extra tip.

So each of us three payed 9€, plus the two our waitress took that amounts to 29 - where the heck did the remaining € go? (That's probably what happened to the Greek national budget... a couple billion times!)

If you (think you) know the answer, please let the others go on guessing, and send me a message with your explanation!