Were you charged Social Security tax you don't owe?
Most nonresident F-1, J-1 and M-1 students don't owe Social Security or Medicare tax on campus jobs, CPT or OPT. Payroll systems often take it anyway, about 7.65% of every paycheck. Enter your W-2 to see what you can get back.
Enter boxes 4 and 6 from your W-2 to see if you're owed money.