We all count on our hands and we use our fingers to represent a digit. When we do this we hold up our fingers to show (1 or 2 etc). Can we ask anyone to unroll their fingers? Like if they are showing one or two fingers only but we want them to show four fingers (to represent number four) so can we say "You are showing two fingers only unroll two more fingers"? Is "Unroll" a correct word here?