you don't it's for the math, because dust is the smallest unit of measurement, and easily put into algebraic formulas example : 116,000 bright dust is about 7,000 engrams however, you get different things from different engrams, sometimes you don't get anything at all you can BUY your items with dust though; it's just used for math purposes, but you could use any of the types of units aka "dollars" "engrams" "dust"