(1) The Commission may reduce the amount of any payment that becomes payable to a person if:
(a) an amount has previously been paid under this Chapter to the person purportedly by way of compensation or payment for treatment provided; and
(b) the amount paid exceeds the amount (if any) that should have been paid; and
(c) the person agrees to the reduction.
(2) The amount of the reduction must not exceed:
(a) if the Commission has not previously reduced a payment under this section--the amount of the excess; and
(b) otherwise--the amount by which the sum of all amounts of excess under subsection (1) exceeds the sum of all amounts recovered under this section.