3 gallons popcorn makes 30 balls. Grandma had an almost identical recipe in her box called Fabulous Popcorn Balls. It called for 1/4 lb. of margarine rather than the butter and had these directions: Bring to a boil in a heavy pan the margarine, Karo and sugar. Add sweetened condensed milk and stir fast to prevent burning. Boil 3 minutes. Pour over 12 to 14 quarts popcorn and leave until just warm; then form into balls. Peanuts may be added. These were so good on Christmas Eve!