recover unaccounted iCloud Document space

On my iCloud account I have 1.5G used for documents (according to the report in iCloud > Settings both on the web and on my phone)

I have about 10% of this that is accountable both in app storage on my iPhone and in my iCloud drive.

I have searched everywhere for a reason for this and have not found anything that works.

How can I see what is taking up the space? How can I clear up space that appears not to be accounted for?

Thanks