It wants only one event per year.
This is a problem with adding stuff like Agricultural or Industrial schedules unless you add the full date of the one or both actual enumerations (which the new form does not) for that Census year.
Also if you find a City Directory entry for a zero-year in the US, it will overwrite a Census enumeration for that year rather than create a new residence event for that year.
This last is particularly confusing since Ancestry.com does not include the County for any of its (beta) City Directory extracts/indexes/add-to forms. So the added City Directory add-to widget will insert by default the faulty Ancestry.com extract instead of the US Census location entry. Grrrrrrrrrrr.