You have a slight mis-conception about what is involved there.
1) If you start collecting SS early, before the full-retirement age for SS, then SS will reduce the next year's actual monthly payout of SS benefits, if your work salary (or self-employment profit) exceeds ~$18.2k for 2020. So, after you file your 2020 taxes, SS will see that you "earned" ~$5k from part-timework, and they won't change next year's monthly benefits ... because it was only 5k. Your 1099-R doesn't affect that.
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2) How much of your yearly SS income is "taxable" is an entirely different situation.
IF you only had SS during the year, and no work income, no 1099-R, no investment income...then none of the SS is taxed......but as you get more income of any other kind during the year, then some of the SS can become taxable....up to 85% of it. So yes, the 1099-R income does affect that. Apparently you've received enough other income such that your SS is getting taxed.
https://ttlc.intuit.com/community/retirement/help/why-did-the-taxable-amount-of-my-social-security-b...
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
