For each month of membership, military, or equivalent membership service not previously credited in the retirement system, a member claiming credit in the elected class shall pay a contribution in an amount equal to the greater of:
(1) eight percent of the monthly salary paid to members of the legislature at the time the credit is established; or
(2) the appropriate member contribution provided by Section 815.402 for a person who holds, at the time the credit is established, the office for which credit is sought.