Cal. Gov. Code § 21054

Notwithstanding any other provision of law, a member or retired member who elected to purchase military service credit under Section 21024 or 21027 on or after January 1, 1999, and prior to January 1, 2001, may, at any time prior to making the final payment for the service credit, elect to have the cost of that service credit recalculated pursuant to Section 21052. If that cost as recalculated under Section 21052 is less than the cost as originally calculated, the member or retired member shall pay the lesser amount, with credit for the payments previously made. However, no refund shall be payable to a member or retired member as a result of the recalculation of cost pursuant to this section.