I spoke too soon when I said this was resolved. It turns out the listing order of categories is alphabetical. I had renamed the categories and that's why they ended up in an order to my liking, although I didn't know that was why until I renamed one again and it changed position.
So, can there be an order other than alphabetical? I'd like my primary (first created) category to be at the top. Is there anyway to do this? Sounds like a minor thing, but it's important to me.