If there is overpayment of a fee as a result of a decision made under the following provisions, the Secretary must, within 28 days after making the decision, refund the overpaid amount:
(a) paragraph 6.2 (3) (b);
(b) if the applicant makes an application mentioned in subregulation 6.2 (4) -- paragraph 6.2 (5) (b);
(c) subregulation 6.3 (2).