That's correct. The vehicle deduction is based on your business miles driven. TurboTax is asking these questions because they are required questions on the tax forms for the vehicle deduction.
To take a vehicle deduction, you are supposed to keep a mileage log. While a lot of people don't follow this requirement, it is required if you are ever audited. A mileage log includes odometer readings, dates, locations and business purpose of the trip. There are many software apps you can get for your phone, which automate this.
If you have 2 vehicles, you'll need to set up two cars. Answer the initial questions in regards to one of the vehicles. At the end you'll come to a summary screen of vehicles entered and you can choose to add another vehicle.
If this isn't what you meant, please provide more info below.
Learn more at the IRS here: https://www.irs.gov/pub/irs-pdf/p463.pdf