(a) Petitions for reconsideration or modification of the decision of the Commissioner in priority or protest proceedings shall be filed within 20 days after the date of the decision.

(b) The Commissioner may consider on petition any matter involving abuse of discretion in the exercise of an examiner's authority, or such other matters as may be deemed proper to consider. Any such petition, if not filed within 20 days from the decision complained of, may be dismissed as untimely.