Yeah the milk frothing steaming minigame was one we kept trying to tweak until we eventually ran out of time. The way it essentially works is there is a perfect green section where you want to keep the steaming temperature in order to reach the target milk volume. The froth is overall a bonus, based on how much time you spent in the green zone. As long as you are hitting the milk volume target you did well, and it unfortunately is easier on some drinks and harder on others.