The day formula stored for this lot is Ascendant plus Venus minus the Lot of Spirit. Spirit is itself Ascendant plus Sun minus Moon by day, and substituting that in gives Ascendant plus Venus minus Ascendant minus Sun plus Moon. The two Ascendant terms cancel, and what is left is Venus plus Moon minus Sun.
That is a real result and not a curiosity. By day the Lot of Eros does not contain the Ascendant at all. It is a function of three planetary longitudes and nothing else, so it does not depend on the place of birth, and it depends on the time of birth only as far as the Moon and Venus move during the day in question.
The practical consequence is unusual among the lots. Most lots inherit the Ascendant's sensitivity and shift a whole sign for every two hours of doubt in a birth time. Eros by day does not. Its terms together move about 13 degrees and 24 minutes a day, so it advances roughly one degree every hour and three quarters, and a birth time uncertain by an hour moves it by less than a degree. A day chart with no recorded time at all still yields an Eros good to within a sign for most of the day.
This holds only for a day birth. A night chart reverses both this lot and Spirit beneath it, and the cancellation does not survive that reversal, so the reduction has to be worked again rather than assumed.