Accumulated retirement contributions credited under this part to the account of a member whose date of birth is changed in the records of the system after December 31, 1979, shall be adjusted to the proper amount based on the correct birth date by either of the following methods:
(a) A refund of the excess contributions plus credited interest from the end of the school year in which contributions were overpaid because of the incorrect birth date.
(b) Payment by the member of the contributions due to the plan under this part plus regular interest from the end of the school year in which the contributions were underpaid to the date of payment.