x1 = m2 [quantity] is x2 = k3 = m3 [number counted] items/units of/in/pertaining to set x3 = k2, on scale x4 = m4 (si'o; default: from 0 representing nothing/no instances of the item, and by (units of) 1 for each additional occurrence if the item is quantized). x1 is countably measurable.
Counting should (ideally) be perfect, so accuracy is identically and mathematically equal to "1"; the scale sets the "counting [off] by units" and most countable things are counted from "0" (meaning nothing/no instances of the item in question) with each additional occurrence of the (quantized) item being represented by an addition "1". See: kamre, kacmre.