"It is not a loan."

That was a hypothetical, that would explain why there might be money in the bank for them to Draw, not having come from Operations.

"It was taken in check form."

That's just the Banking. That doesn't change the Accounting of that draw. Cash, check, chickens; it's Asset removed.

"They just provided some additional income."

Just now, in May of 2021, for 2020 business?

"So this makes the capital account not a negative and they are being taxed on 28191(new line 1 on K1) not 13199 (original line 1 on K1)...sighhhhh love tax season"

Or, they had a tax loss for the year, and the $13k was not wrong. Let's examine a theoretical: "So that's why I thought that at least 20000 shoudle be taxable not just the 13199."

You keep thinking their Activity of taking money is the same as having income. You are skipping over that this is a Pass Through Entity. They don't get "income" from the business Bank. The Business makes income or not. Cash moving is neither income nor expense until you know what it was used for or why it moved; Cash Flow = it's just moving. Removing your own asset from your own partnership is not a Business activity. There is no new income or new expense.

Let's pretend they net $40,000 of new cash by year end. Meanwhile, you are working on the taxes and there is some depreciation and other credits and deductions. Those are what I call in class: Not real dollar expenses. For instance, Mileage Allowance is a good example. In my pretend scenario, let's operate a delivery van. Even taking the operating expenses into account, there might be other equipment with depreciation and even bonus depreciation, which is Not Real Dollars. We didn't spend it; the tax return provides it as a deduction, though.

So, you are not going to successfully back-calculate income using their Draws. Because you are trying to include things that do not relate.