If an employee, or an employee’s spouse or children, receives compensation under any workers’ compensation or occupational diseases law, the benefit payable under this Article shall be reduced by the amount of the compensation so received if the amount is less than the annuity or benefit. If the compensation exceeds the annuity or benefit, no payment of annuity or benefit shall be made until the period of time has elapsed when the annuity or benefit payable at the rates provided in this Article equals the amount of such compensation. However, the commutation of compensation to a lump sum basis as provided in the workers’ compensation or occupational diseases law shall not increase the annuity or benefit provided under this Article; the annuity or benefit to be paid hereunder shall be based on the amount of compensation awarded under such laws prior to commutation of such compensation. No interest shall be considered in these calculations.