You are using self employed (maybe a rideshare driver) so I will assume you are correctly counting your miles. The 9,000 mileage deduction reduced your income by 9k not your tax liability.
It would reduce your self employment tax liability as well as reducing your federal tax.
Disclaimer: Not a tax professional. Information gathered from internet links. Anything dated in June 2019 was posted in prior years and is before the 2019 limits and changes.
