Retirement tax questions

I am confused by the Self-Employment Tax Deferral.  When going through the guided questions, it asked if I would like to defer these tax payments.  I selected No, but was still asked to enter an amount during the final checks in line 18.  Based on the answers on this topic, you would think TurboTax would automatically enter $0 on Line 18.  Regardless of selecting Yes or No for deferred payments, I received a message saying I was not qualified for deferred payments (since I am receiving a refund).  Since, I did not understand what amount should be put on line 18, I entered a dollar amount.  It now looks like it is setting up a deferred payment.  How do I go back into the form to change line 18 to $0?  Changing the answer in the guided questions does not change the value on line 18.  I am using the Online version of TurboTax.