YOU create the 4 digit code to lock the infotinament. So if you do valet parking, they can't go into the infotainment. Once you get the car back, you put in the 4 digit code that you created and it'll unlock the infortainment
As others said, this is a one-time code. When you enter Valet mode, you "lock" the car in Valet mode by creating a pin. It works just like those lockers you rent at waterslide parks. When you enter the pin again, it unlocks and returns to normal.