Not sure how you arrive at the "user error" conclusion. It's definitely not a data entry error. Here is why.
IT-203 Line 18 was correct on the "Federal" section but incorrect on the "New York State" section. There is no separate data entry for the "New York State" section. It is derived, by TurboTax, from the federal return. It seems that TurboTax did not code the New York State guideline correctly. It's a programming error.
The same problem exists with the IT-558. The incorrect entry is not some data separately entered by the user. It is derived from IT-203 on which it is correct. Again, it is a programming error.
Sadly, the "100% Accurate Calculation Guarantee" does not guarantee any accuracy. It is not even applicable unless one had to pay a penalty or interest as a result of a calculation mistake by TurboTax. There is no redress for the additional time spent by the user figuring out the problem or for submitting an amended return. So, the text of the guarantee is somewhat misleading.
