Once upon a time, a Customer called to complain that our beverage cans held too much beer. This could be a problem because the Benevolent Government, ever alert to our well-being, or at least to their own revenues, taxes alcoholic beverages on the nominal package volume. A 12-oz. can is presumed to hold 12 oz. of beer at 3.4% alcohol by weight and is taxed accordingly. If it holds more than 12 oz. then the brewer is giving away free beer and (more importantly) not paying taxes on the extra fraction of a percent of an ounce. ATF has never reconciled with the end of Prohibition.
The primary control measurement is called "Overflow Capacity," which measures the volume of fluid the container can hold up to the tippy-top. The ASTM "Wet Fill" method of making the measurement proceeds as follows: