A motion for reconsideration may be filed by either party. It shall set forth specifically the grounds relied upon to grant the motion. The motion must be filed within 30 days from the date of the receipt of a copy of the decision of the Board by the party filing the motion. An opposing party must file any cross-motion for reconsideration within 30 days from its receipt of the motion for reconsideration. Extensions in the period to file a motion will not be granted. Extensions to file a memorandum in support of a timely-filed motion may be granted.