The IRS doesn’t reimburse you for the mileage you claimed on your Schedule C.
The mileage amount that you’ve calculated merely offsets any self-employment income that you’ve made. Self-employment tax is then calculated on your net self-employment – your self-employment income, minus your self-employment expenses, which include your mileage expenses.
If your tax return indicates that you’re getting a $1,400 refund, then that’s all you’ll get.
Please see the TurboTax Help article Can I deduct mileage? for more information.