Yea, zeds picture only shows him having 4 fingers. An index, middle, ring, and pinky.
I still think its a joke. Maybe its that one joke "how many fingers do i have?" and they say "10?", and you say, "No, i have 8 fingers and 2 thumbs" . He has 4 fingers and 1 thumb on his left hand.
Please BBB, i love steve vai's music and that makes him my guitar idol. but im not going to believe that the reason he plays so good is because he has 5 fingers on his left hand (and one thumb). He is musically inclind and a prodigy. And he used to practice for days on end till he got everything right.