Transferring data from last year's return is handy for reducing the amount of manual entry you have to do. But it can result in a lot of duplicates if you download data from your financial institutions and/or import from Quicken.
For example, TurboTax asks me whether I want to transfer several Forms 1099 (INT, DIV, etc.) from last year. It asks the question "Did these still apply in 2016?" Well, sure they did, but I'm going to download all that data from my bank and brokerage. I therefore tell TT "No," these don't apply, avoiding later duplicates.
Similarly in the Deductions section, TT asks me if last year's charitable donations still apply in 2016. Mostly they do, maybe some don't. But I'm going to import that information from Quicken, so, again, I tell TT they don't apply in 2016.
