you mean the amount on line 3 of 1099-Div. these are return of capital dividends which lower your tax basis in the related stock. They are not taxable as long as they don't reduce your tax basis in the stock below zero.
in theory, the reporting entity reduces your tax basis which you might not see until several months later on your monthly statements. if your basis goes negative the reporting entity should report this on the 1099-B. if you don't enter the amount on line 3 no harm is done because Turbotax does not use this amount for anything.
