With "Show Remaining Entrances" On, removing a custom marker removes an entrance

[Alaszun]

If I add a custom marker to something and later remove it, it decrements the entrance counter, even though adding a marker doesn't increase it. This can make it possible to end up in negative entrance values, even when there are entrances left.

IMO, the right way to deal with this is to only decrement when a green square is cleared instead of anything, although I could see wanting to add an entrance if you add a marker as well.