When carbonating a beer the "volume" referred to is targeted volumes of CO2, not % alcohol by volume. What it means is volume of CO2/ volume of beer. So a typical beer may be said to have around 2.5 vols., often written 2.5 v/v, of CO2. This means a liter of beer will have 2.5 liters (as would be measured at standard temperature and pressure, or about 4.94 grams) of CO2 dissolved in it. Why this confusing system is used is a mystery. But I hope that explains it for you. The calculator in the link above will help you determine how much priming sugar you need to get the desired level of carbonation. It takes into account the small amount of CO2 remaining in the beer from fermentation, which varies depending on temperature. What level of carbonation you target is your choice. Welcome to the hobby!
