It's not stuff because it's a verb not a noun. To hexadecimal is to cast a cantrip on a real number, attacking it at one of the digits after the decimal point. This usually causes the poor benighted number to trip (but not always, since it's a cantrip not a musttrip) resulting in an unpleasant flattening of part of its anatomy when it hits the ground (such flattening is known amongst numerate spell-casters as a rounding error).