Stella, it is quite simple that when we bid high, we have a high chance that our product will be shown on the top of the page, and more likely, we have a chance to get sales. In any case, when you lower your bids, there will be some other sellers who have set high bids. Amazon will definitely prefer those sellers to show on the top of the page, and due to the lower bids, your ad will be shown on the 2nd or 3rd page or at the end of the 1st page. Therefore, your orders have been dropped. As a result, whenever you attempt to lower the bids, only lower a few cents. So, your ranking would not be diminished.