Line 8a of my schedule A is 13,396. The interest from my three 1098s (1st home, 2nd home, and HELOC). add up to 19121.15. The HELOC is less than $100,000 and the total of the three loans is less than $750,000. Where does the $13,396 come from?
If you right-click on the value on Line 8a and click Data Source, you will be able to navigate to the worksheet that calculated this number. It might provide further detail as to how the TurboTax software arrived at that number based off of your entries.