IF YOU DID NOT FINISH IN THE BAY, WHAT DO YOU DO?
Are you on the line or just outside? If you are on the line it should be a driving fault (not serious). If you are outside of the bay, it is a serious driving fault and you will fail. Unless you fix it.
Full POM routine, select Reverse and if it is safe reverse out of the bay in a straightline. Reverse as far as you need to so that you can see the bay lines of the bay you want. Stop.
POM routine again and drive forward steering into the bay you want. Secure the car. Check you are in. One correction is generally accepted by examiners.
NOW YOU ARE IN THE BAY, HOW DO YOU REVERSE OUT OF IT?
DIFFERENCES BETWEEN AUTOMATIC CARS AND MANUALS