Don't pay it. It is illegal to do that

 

Print this form and check item (J).Send your compalint form to department of labor

(j) Employer imposed an illegal penalty (as opposed to liquidated damages permissible under state law) on nonimmigrant worker(s) for ceasing employment with the employer prior to a date agreed upon by the nonimmigrant worker and the employer.

http://www.dol.gov/whd/forms/wh-4.pdf