After an appropriate salary is determined to be used in calculating the cost of military service credit, the calculation shall be made as though the member earned such salary during the period being established and contributions shall be determined on such salary and interest shall be computed from the date such service was rendered to the date of payment.
Ga. Comp. R. & Regs. R. 513-5-1-.35
O.C.G.A. Sec. 47-3.26 .