Schedule CA, taxable interest subtraction

Is there a way to see how TurboTax computes the entry for California Schedule CA, line 2, column B Taxable Interest Subtraction? In my case it seems to come exclusively from the Interest and Dividend Adjustments Worksheet line 1, Bonds or obligations of the United States or any of its territories. I expected this to come from form(s) 1099-INT, Box 3 (Interest on Treasury obligations), less Accrued (Treasury) interest paid, less (maybe) Treasury bond premium reported to me, but I can’t make the numbers add up; TurboTax seems to be giving me a larger subtraction than I deserve.

Thanks, DW