For any generational member, "credited service" means the sum of the following:
(1) Years of service, or fractions thereof, for which a member contribution was made to the system;
(2) Any period of authorized leave of absence or sick leave with pay, for which a deduction for any member contribution was made, deposited, and credited to the fund;
(3) Any period of authorized leave of absence or sick leave without pay or temporary layoff, during or for which a member obtained credit by payments to the fund made in lieu of salary deductions; and
(4) Any period during which a member is on an authorized leave of absence to enter military service, if the member fulfills the requirements set forth in § 3-12C-514.