The claimant or any other interested party may file an appeal from an initial determination, redetermination, or subsequent determination not later than ten days after the determination was mailed to his last known address. The term "any other interested party" means the claimant’s last or separating employer and any employer whose account may be affected by the adjudication of the claim. If an appeal is filed with respect to a matter other than the weekly benefit amount or maximum amount of benefits payable and the appeal tribunal affirms a determination allowing benefits, the benefits paid before the decision disallowing benefits shall not be recovered from any claimant regardless of any appeal which may subsequently be taken to the extent that these benefits are not charged to the account of any employer.