Each justice or judge who is a member of The Uniform Retirement System for Justices and Judges upon retirement after June 30, 2004, shall be entitled to receive as retirement compensation, until changed by the Legislature, an annual amount, each monthly payment of which shall be in an amount equal to four percent (4%) of the average monthly salary received by him or her as a justice or judge based on the highest three (3) years of active service multiplied by the number of total years of service and reduced according to the elected survivor option, if any. The amounts of compensation reported to the Oklahoma Public Employees Retirement System for the Uniform Retirement System for Justices and Judges, by the Office of Management and Enterprise Services prior to June 30, 2004, may be conclusively presumed as valid regarding the source of the compensation reported as salary for purposes of the accuracy of the employees' contributions and the computation of salary for the calculation of benefits. This presumption shall not include any computation error made by the Office of Management and Enterprise Services or the Oklahoma Public Employees Retirement System on behalf of the Uniform Retirement System for Justices and Judges. Provided, however, that no justice or judge retiring after June 30, 2004, may receive a monthly retirement benefit in excess of one hundred percent (100%) of the average monthly salary based on the highest three (3) years of active service and found applicable to such justice or judge at the time of retirement. Retirement compensation shall be payable monthly out of the State Judicial Retirement Fund by warrants prepared by the Executive Director of the Public Employees Retirement System and issued by the State Treasurer.