New York Consolidated Laws, Village Law - VIL § 3-304 Changing number of trustees

a. If the number of trustees be increased, the additional trustees shall be elected at the next general village election when trustees are regularly scheduled to be elected.  At that election half of the additional trustees shall be elected for a single term equal to half of the full term for which said office is regularly scheduled to be filled and the other half for a full such term.  At all subsequent general village elections such offices shall be filled for full terms.

b. If the number of trustees be reduced, no trustees shall be elected, other than to fill an unexpired term, until by expiration of terms of office the number of trustees in office shall equal that prescribed by such resolution.  Thereafter at the next general village election one-half of such prescribed number of trustees shall be elected for a single term equal to half of the full term for which said office is regularly scheduled to be filled and the other half of such trustees shall be elected for a full term.  At all subsequent general village elections such offices shall be filled for full terms.