Notability Storage In iCloud cannot be found

Hi there. I am having an issue with Notability. I have opened settings in the app and selected that I no longer want to use iCloud. I then said that I wish to keep a copy of my files on my iPad. Now I wish to delete the files Notability put into my iCloud. However, although settings tells me Notability is using 5Gb:

When I look in iCloud Drive, there are no sections for Notability:

How can I delete the storage that Notability is using on iCloud?