Prior to the 12th Amendment, each elector had two electoral votes for president rather than one for president and one for vice president. The candidate with the most votes became president and the runner up became vice president. I don't know how Delaware chose electors, but there were three. Each of them cast one vote for Washington and one for Jay. Nationally there were 69 electors, and each of them cast one vote for Washington. From what I've read, even before the election there was no question that Washington would be president, so the John Jay votes were understood to be votes for Vice President.