The commissioner shall grant an interim rate, in an amount as determined by the commissioner, if the commissioner makes a finding that the corporation has made a convincing showing that there is probable cause to believe that the failure to grant the interim rate will result in an underwriting loss for that line of business for the period for which rates are being requested. If the final rate determination results in approval of a lower rate, appropriate refunds or adjustments, as determined by the commissioner, shall be made to reflect payments made in excess of the approved rate.