I contributed $23K to my solo 401k as employee and will contribute $12K as an employer based on TurboTax's calculation but when I input that, it taxes owed doesn't lower?

I'm in the section where TurboTax asks you for Self Employed Retirement Plans if I contributed to a traditional individual 401k plan. I selected yes. I put $23K into elective deferrals since that's what I contributed as an employee and now would like to max out the employer's side which is 20% of net income I believe. Turbo tax has a button I can click for them to calculate what the max contribution I can make is which comes out to a little over $12K. How come now when I add that 12K to the "employer matching (profit sharing) contributions" box, it doesn't lower my taxes owed at all? This should bring it down no?