“Relation of Earnings to Insurance: If the total monthly amount of loss-of-time benefits promised for the same loss under all valid loss-of-time coverage upon the insured, whether payable on a weekly or monthly basis, exceeds the monthly earnings of the insured at the time disability commenced or his or her average monthly earnings for the period of 2 years immediately preceding a disability for which claim is made, whichever is the greater, the insurer will be liable only for such proportionate amount of such benefits under this policy as the amount of such monthly earnings or such average monthly earnings of the insured bears to the total amount of monthly benefits for the same loss under all such coverage upon the insured at the time such disability commences and for the return of such part of the premiums paid during such 2 years as exceeds the pro rata amount of the premiums for the benefits actually paid hereunder; but this provision shall not operate to reduce the total monthly amount of benefits payable under all such coverage upon the insured below the sum of $500 or the sum of the monthly benefits specified in such coverages, whichever is the lesser, nor shall it operate to reduce benefits other than those payable for loss of time.”