Allowable expenses are those reasonable and customary expenses that the insured incurred and that are covered under the group expense plans. The secondary provider then looks at the amount the primary provider paid. If payment of the full benefit amount provided by the secondary plan would result in the insured receiving more in benefit payments from both plans than the total amount of allowable medical expenses, then the secondary plan pays only the difference between the amount of allowable expenses incurred and the benefit amount the insured already received from the primary plan.