For a period of 60 days after the effective date of this Section, a person may transfer to a fund established under this Article up to 10 years of creditable service accumulated under Article 5 of this Code upon payment to the fund of an amount to be determined by the board, equal to (i) the difference between the amount of employee and employer contributions transferred to the fund under Section 5-237.5 and the amounts that would have been contributed had such contributions been made at the rates applicable to an employee under this Article, plus (ii) interest thereon at the actuarially assumed rate, compounded annually, from the date of service to the date of payment.