What is the "Ready to publish" card?

The first card on the left. It says how many mazes are made and checked ("every cell reachable, exactly one way from the start to the finish, and the difficulty measured by a simulated solver. None repeats another maze of this book."), the page count at your trim with the inside margin, and that the walls are 0.75 pt or heavier and the corridors 2 mm or wider. Any problem is listed in yellow, and while one remains, Export is greyed out. Notes (tips that do not block the export) are listed under the problems.