The Screen Time passcode is an optional feature of iOS 12 and 13 that can be used to secure the Content & Privacy Restrictions. Once the password is set, iOS will prompt for the Screen Time passcode if an expert attempts to reset the device backup password (iTunes backup password) in addition to the screen lock passcode. As a result, experts will require two passcodes in order to reset the backup password: the device screen lock passcode and the Screen Time passcode. Since the 4-digit Screen Time passcode is separate to the device lock passcode (the one that is used when locking and unlocking the device), it becomes an extra security layer effectively blocking logical acquisition attempts.