It’s not an extra finger, it’s the skin on the edge of the hand that is folded because of the awkward position of the hand. It’s an unfortunate crop, though, because an untrained eye might mistake that portion as an extra finger.

At first I was wondering what the numbers were for... then I realised you thought palm flesh was a finger and I pitied you instead. The clue is in the lack of an extra knuckle.

If the end result is less shrill shrieking on the internet, good.