They may have employee numbers but as far as their seniority is concerned it's their first day of class. Seniority in class is determined by the last 4 of your SSN with 0000 being senior and 9999 being junior. The cadets are the exception to that - they are first in class followed by everyone else. Considering huge classes are being run every two weeks it'd certainly be nice to be ahead of a few more people but it's not a game changer by any means.