The limitations on the number of terms prescribed by Section 2 of Article IV, Sections 2 and 11 of Article V, Section 2 of Article IX, and Section 17 of Article XIII apply only to terms to which persons are elected or appointed on or after November 6, 1990, except that an incumbent Senator whose office is not on the ballot for the general election on that date may serve only one additional term. Those limitations shall not apply to any unexpired term to which a person is elected or appointed if the remainder of the term is less than half of the full term.