Class H credited service includes:
(1) Service by an employee rendered since becoming a class H member;
(2) Service credited under part II as a class A member or a class B member and converted to class H credited service pursuant to section 88-322(b);
(3) Service credited under part VII as a class C member and converted to class H credited service pursuant to section 88-322(a);
(4) Service in the armed forces as provided by subpart E of part II;
(5) Mandatory maternity leave as provided in part II; and
(6) Unused sick leave as provided in section 88-63; provided that any additional service credit shall not be used in determining eligibility for retirement or for any other purpose as a class H member.