Is this a salary advance or a sign on bonus?

f I signed an employment agreement which says my annual salary would be X number of dollars annually (say 25,000), payable on bi-weekly basis etc. Also in separate section states a "Sign-On Salary Advance" of x number of dollars (say 5,000) in lump sum...should the amount of the check be for 1. the whole 5,000, 2. 5,000 minus PAYROLL taxes or 3. 5,000 minus BONUS tax rate? In any of the above scenarios would my pay rate for subsequent pay checks be based on a rate of $20,000? (The 25k minus the 5k advance) Any help would be greatly appreciated. :)