Why is my refund so low?

Please be advised that the refund is the taxes that you have overpaid only, not the total tax you have paid during the year. 

If you are unsure about the refund you are seeing on Step 7 - Summary, you can go back through the steps and check that the information you provided on Step 3 - Let's talk money is correct.

If the details are correct, then that is the refund you would receive. Don't forget that as a nonresident you are not taxed the same way as the residents and the deductions you can use are very limited.