1040 line 12 is the Standard Deduction or your itemized deductions whichever is more. Nothing to do with Captial Gains or Schedule C. Capital Gains show up on 1040 line 7. Schedule C Net Profit goes to Schedule 1 Line 3 then to 1040 line 8.
What are you trying to do? Do you want to pay self employment tax on it instead of the Capital Gains rate?
