Line 6 on the Social Security Benefits Worksheet is showing $300. The instructions indicate this value is calculated by adding Schedule 1 lines 10 through 19 plus any write-in amounts on Schedule 1, line 22. I have nothing entered in any of those lines on Schedule 1. Where is the $300 coming from?
I just called TurboTax Support and the wording on the Social Security worksheet seems to be confusing or incomplete. It (also?) includes line 10b of your 1040-SR. In 2020, you are allowed to take a $300 deduction for charitable contributions even if you take the standard deduction. That is what showed up in my case. The $300 is actually reducing the amount from line 5 on the worksheet. Hope this helps.