I am see recipes for a lot of 6 gallon batches out there. I have a set up where I am filling 5 gallon corny kegs (like most I imagine). What's up with the 6 gallon batches? Folks bottling a gallon? This doesn't have anything to do with pre-boil volume does it? Do most typically alter the 6 gal recipe to fit a 5 gal volume?