Filing CA state 100S after 1120S, Turbotax says "Form 100S p4-6: Schedule M2 Line 3 total shouldn't be less than or equal to zero"

Hi I'm in the final check up for my CA State filing. But the software always errors out at Schedule M-2. My current line 3 is "Other additions", where column (a) is "AAA", column (b) is "Other Adjustments". In Line 3, it automatically fills in "Tax Exempt Interest", and the value filled in column (a) AAA and column (b) Other Adjustments are both 0 right now.  So the total other additions of Line 3 is 0 in column (a) and (b). But it gives me red color and I can't proceed. The software says the total shouldn't be zero. What's going on here and where could I fill wrong? Thank you!