I am amending a tax return for 900 1099nec, it shows I need to pay 361. but my tax bracket is 32% and maxed out social security tax. why I need to pay > 40% of 900?

I missed on 1099 nec form this year. I believe my tax bracket is 32%. so I shouldn't need to pay extra 361 for 900 income. I wonder how is it get calculated? Is it a bug for turbo tax? My taxable income minus long term capital gain should fall into 32% bracket. and I have max out my social security payment. I might need to pay medical tax of 2.9%, but that should be 34.9% total, right?