An Airforce personnel who just passed out 4rm the Airforce training, told me that a girl who passed out with him is his senior based on their Service Number. Pls, someone explain and give an example or an illustration of the seniority. Thanks.

Why don't you asked him to explain the reason of it to you.
The said girl may be a regular(NDA) or DSSC. They will firstly undergo training with the army before going for their own force/unit training which do usually coincidence with yours.

dacillin:
Why don't you asked him to explain the reason of it to you.
The said girl may be a regular(NDA) or DSSC. They will firstly undergo training with the army before going for their own force/unit training which do usually coincidence with yours.

He told me something related to serial number. He told me that there was a girl that Passed out with them in the Airforce that he likes that he wants woo. He told me that the girl is his senior based on their Service Number. So, i want to know whether it's base on the number that comes first.