Try using the steps to get back to your vehicle expenses on Schedule C to change your mileage.
To Enter Your Business Vehicle Mileage:
1. Select "Business" at the top of the screen
2. Choose "Continue", then "I'll choose what
I work on"
3. Select "Start" next to "Business Income
4. Select "Edit" next to your business name
5. Scroll down to Business Expenses
6. Now select "Start" next to "Business
7. Select "Edit" next to your vehicle(or enter the information
when asked to)
8. Continue until you arrive to the screen asking for mileage and
make any changes
For more information on claiming your mileage visit this link:
Business Use of Vehicles