When I enter Individual 401k "elective deferrals," my tax due decreases as one would expect. But when I enter "employer matching contributions," it does not go down. Why?

I am self-employed and have a solo 401k.

When I add the proper amount to the "elective deferrals" box, the "federal tax due" amount decreases. This makes sense since this is tax-deductible.

However, when I add my "employer matching (profit sharing) contributions," this has no impact on the "federal tax due" amount.

My understanding is that, for self-employed people, both employee and employer 401k contributions are tax deductible. Is this incorrect?