All other parties may give notice of cross appeal and set out exceptions which shall set forth specifically the grounds on which the said party considers said decision or order to be unlawful, unjust, unreasonable or unwarranted, and including errors alleged to have been committed by the Commission. Such notice of cross appeal and exceptions shall be filed with the Commission within 20 days after the first notice of appeal and exceptions has been filed, or within such time thereafter as may be fixed by the Commission, not to exceed 20 additional days by order made within 20 days of the first filed notice of appeal and exceptions.
N.C. Gen. Stat. § 62-90