They are ordered as in K2, but only within categories. This means that items are first ordered by category (as in K2 category ordering) and then items are ordered by K2 item ordering but within the categories.
You can't order all items arbitrarily without taking the categories ordering under consideration.
- Category 1:
-- Item 1
-- Item 2
-- Item 3
- Category 2:
-- Item 1
-- Item 2
-- Item 3