As 237SJ says, heavy drinkers build up a tolerance to alcohol (while, at the same time, doing a great deal of damage to their bodies).
For example, drinking a single bottle of whiskey can (and does) kill some people who aren't used to consuming alcohol. However some experienced drinkers can get through 3 or 4 bottles of whiskey in a day. Given that, in terms of alcoholic content, 1 bottle of whiskey roughly equals 3 bottles of wine, the figures you quote seem to be possible for an experienced drinker.