When liters are converted to wine gallons, the proprietor must multiply the quantity in liters by 0.264172 to determine the equivalent quantity in wine gallons. If cases contain the same quantity of spirits of the same proof in metric bottles, the proprietor must convert the cases to U.S. units by multiplying the liters in one case by the number of cases to be converted, as follows:
(a) If the conversion from liters to U.S. units is made before multiplying by the number of cases, the quantity in U.S. units must be rounded to the sixth decimal; or
(b) If the conversion is made after multiplying by the number of cases, the quantity in U.S. units must be rounded to the nearest hundredth. Once converted to wine gallons, the proprietor must determine the proof gallons of spirits in cases as provided in § 30.52 of this chapter.