The test did exactly what is says on the tin - Assessed your ability to check information in an alloted time.
Are you saying that if you did not suspect duplicate codes and found the matching one was the first code on the list, you would not have checked the others? If so, then that means you would not be checking correctly.
You did what was required, but you were unable to do it to the required standard. Nuff said.
Try again next year.