You will see these valet at some five star hotels and restaurants. Usually, these guys are professionals and makes lots of money from parking car. You can trust them with your car as that is their job and they don't want to endanger their job.
The idea of this game is to drive and park the car according to their numbers. The costumer will say the number to which you will park the car. Afterwards, they will come back and you will get paid for giving them their car back. Try not to bump this car or it will be deducted on your fees.