If the trial court shall, upon a motion for new trial, find the damages awarded by a jury to be so excessive or inadequate as unmistakably to indicate that the amount thereof must have been the result of passion or prejudice, the trial court may order a new trial or may enter an order providing for a new trial unless the party adversely affected shall consent to a reduction or increase of such verdict, and if such party shall file such consent and the opposite party shall thereafter appeal from the judgment entered, the party who shall have filed such consent shall not be bound thereby, but upon such appeal the court of appeals or the supreme court shall, without the necessity of a formal cross-appeal, review de novo the action of the trial court in requiring such reduction or increase, and there shall be a presumption that the amount of damages awarded by the verdict of the jury was correct and such amount shall prevail, unless the court of appeals or the supreme court shall find from the record that the damages awarded in such verdict by the jury were so excessive or so inadequate as unmistakably to indicate that the amount of the verdict must have been the result of passion or prejudice.