one thing I've learned over the years is that brewers and distributors can
tell you how much liquid they put in a keg. NO ONE can tell you exactly how
many beers will come out.The temp(outside and in the cooler), the age of the
beer, the amout of gas, the length of the tube,the temp,size and shape of the
glass the angel it's held and about 1000 other things infulence the amount of
foam genereated and wasted.
Dennis