In reality, it's not about the issue, it's that returning the BTC is as if they never gave 30 BTC but only 27 BTC, effectively paying 9 each and a tip of 2 BTC.

Wait, where’s that 1 BTC now? 😱😱😱

Three people decide to split the bill at a restaurant. The waiter tells them the total is 30 BTC, so each person pays 10 BTC. Moments later, the waiter realizes the bill should have been 25 BTC, not 30 BTC. To fix his mistake, he brings 5 BTC in 1 BTC coins back to the table, but realizes he can’t split the coins evenly among the three. Since the customers don’t know they overpaid, he decides to give 1 BTC back to each of them and keep 2 BTC for himself.

Each customer gets 1 BTC back, meaning each of them actually paid 9 BTC, for a total of 27 BTC. The waiter kept 2 BTC. So 27 BTC + 2 BTC = 29 BTC. But the customers originally paid 30 BTC — what happened to the missing 1 BTC?"

Did you find it? Congratulations! 🥰
$BTC