Stars

I am a new NS1 and have seen this once or twice in my battalion and just now saw it on the subreddit, but what does the star above the J-Bar mean? I know that the stars above the ribbons are called Designation Stars or D-Stars and they symbolize how many years you have been in the corps, but I have no clue what the star on the collar above the J-Bar means. It would be a great help if somebody could tell me because it is just about the only thing on the uniform I do not know.