How does the front desk know that the guest has used the paid goods placed in the room?

Most of them are counted by the room cleaner when cleaning every day. At least, guests will count when they leave the store; So at the front desk, you will see or hear the cashier waiting for the reply from the cleaning staff.

There are a few hotels whose refrigerators have sensors and are connected to the front desk. There will be a charge when moving, but not much.