Questions on the forms must be answered with accuracy to avoid complications in the future.
If that is your SS number, then state so, if not then do not. Do you have an SS card with the number on it, you could verify with the SS Administration.
If unsure you can provide this information later to the immigration.
Make a request for an expedited interview and state your reasons.
In most cases, immigration are well acquainted with the military demands and will accommodate accordingly if possible.