So now you've opened the "toolkit" approach to macro-evolution. Can have another finger, 'cuz the codings already there. Can have another eye. Can have another knuckle. Can have a longer leg, a shorter leg, a bigger ear, a smaller ear. Can have a moved nose. Can have two legs or four legs. Can have enlongated toes that look like fingers, etc etc.
You've just admitted to the last 200 million years of macro evolution -- because many of modern physical structures existed in various forms back then.
Where? In the parent DNA? One parent or both? Or all humans have coding for six fingers and toes? What? What's the basis for your claim? The Bible?
Uh, you have fingers, right (I'm just guessing)? So unless you're using some odd sort of input device, you obviously have information for fingers in your genome.
As for having an extra one, that's most likely a result of an errant cell separation during prenatal development--not a genetic trait. A cell which was supposed to develop into a finger split and the two cells got separated, each becoming a separate finger. Since such a trait is not genetic, it cannot be inherited and is thus unlikely to play a role in evolution (unless certain genetic traits make such splits more or less likely to occur).