YSK: Amazon keeps delivery instructions/notes until you delete them. Delivery instructions will look blank until you click on it to add and then will show previous note.
from /r/YouShouldKnow
YSK：亚马逊会保留交付说明/注释，直到你删除它们。送货说明看起来是空白的，直到你点击它来添加，然后会显示以前的注释。