I have such a minor additional comment.
I had a case where I put in all my items in the sell area, only about 30/40% of the area was covered but all the criteria were met. In this case, even though I don't have any items, the game shows me a message indicating that I should try to fill as much of the area as possible. The game should not show this message when I don't have any additional items to put in, as it is asking me todo an impossible thing.