The sum of Col c&d will always match the sum of Col a&b, and they're straight calculations.
Are Columns a and b correct? 'a' is what you entered this year, but is also impacted by Form 6198 if that's in play for you. Right clicking the cell will show you the source. 'b' is just prior year's carry over.
Col c should only be non-zero, and negative, if 1) a+b are negative AND 2) you have passive income showing up elsewhere in c which is allowing TT to release some of your passive losses rather than suspending them.
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**Note also, I'm not a Tax Preparer/CPA. Just a volunteer, seasoned, TurboTax user.
Use any advice accordingly!