If your federal taxable income without the employer profit sharing contribution is already zero, adding the profit sharing contribution will not further reduce your taxable income or your tax liability. However, you'll still be subject to self-employment tax. Self-employment tax is determined by your net profit from self-employment and is not affected by any deductions that you claim on your federal tax return.
Also note that TurboTax has not yet been updated with the 2020 elective deferral limits and is still using the 2019 limits. Since you made an elective deferral of $19,500, TurboTax is presently (version R14.1) calculating an incorrect self-employed retirement contribution in your case.
