It sounds like you're being asked this in the review screens, so I'd recommend going back to the initial entry and making sure to enter this info there as asked. I'll include instructions below.
Also, you must enter the mileage under "business" not commuting miles, on the entry screen for the mileage. The software also does ask about the vehicle, per the IRS rules, but again I'd recommend entering this in the initial entry area. To do so:
- Login and click Take me to my return
- Select the Federal Taxes tab and then click the Deductions & Credits tab below it
- Scroll down to the Employee Expenses section and click the blue hyperlink Show more
- Click Start/Revisit next to Job Expenses for W-2
- Next you'll be on a summary screen and see your occupation, which means your job during 2016. Click Edit next to this Occupation.
- You'll need to Continue through these screens until you come to a vehicle expense summary screen. Here you'll see your mileage listed by the vehicle. You can click Edit to review your entry. If you're having any problems, sometimes it's easier to + Add another vehicle to make changes and Delete the old entry (from the summary screen).