Menachot 105 - One Who Promises a Flour Offering
If one promises a "tenth" of an ephah, he should bring one "tenth", if he promises "tenths," he should bring two, but if he says, "I specified the size but forgot," he needs to bring the largest possible offering, 60 tenths, or about 300 pounds. In this last case, he states, "The amount that I promised in my vow is found within these 60 tenths and it goes for the fulfillment of my vow, and the rest I am bringing as a free-will offering."
Art: Charles Meer Webb - A Satisfying Meal
