Mich. Comp. Laws § 38.1613a

Sec. 13a. If a change or error in the records of the retirement system results in a retirant, retirement allowance beneficiary, or refund beneficiary receiving from the retirement system more or less than the retirant, retirement allowance beneficiary, or refund beneficiary would have been entitled to receive had the records been correct, the retirement system shall as far as practical correct the error, and may adjust the payment to provide an actuarial equivalent of the benefit to which the retirant, retirement allowance beneficiary, refund beneficiary, estate, or legal representative was correctly entitled. The retirement system shall not make an adjustment in benefits for an error totaling $20.00 or less annually.