Notebooks on mobile - how are they sorted?

Notebooks on mobile - how are they sorted?

There should be a sorting option for notebooks (as well as notes) on mobile. At the very least I'd like the default sorting to be "Date Modified  (newest first)". Currently, I'm a bit confused as to how my notebooks are sorted. They are clearly not sorted alphabetically, and when I modify a note in notebook X, it doesn't get to the top of the list. 

So how are they sorted? Anyone here from Zoho?