IIRC some cultures use a nifty method where the right hand is the ones column, the left hand is the tens column, and the thumb indicates five (sort of like an a

IIRC some cultures use a nifty method where the right hand is the ones column, the left hand is the tens column, and the thumb indicates five (sort of like an abacus). Then each hand can represent 0 to 9, and together they go to 99.