this is turning into a bit of a carriwitchet, but when you think about it, defining ullage as 2. the amount of goods lost by passing through the sides of a bag. involves--granted, in absentia--the measurement of the 'lost' wine itself, as evidenced by the space created in the vessel. it's kinda a 'glass half empty' conundrum, but if you buy into that theory, it would stand to reason that the dregs at the bottom of a glass of wine as it's whisked away from the table is indeed the ullage of that which should theoretically have arrived into the vessel of one's body.