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：亞馬遜會保留交付說明/註釋，直到你刪除它們。送貨說明看起來是空白的，直到你點擊它來添加，然後會顯示以前的註釋。