Used storage quota error on Ubuntu

Used storage quota error on Ubuntu

There seems to be some errors concerning how much file space is used (Zoho  Docs 1.5.3 /Linux).
My desktop icon says "Used 4.9 GB of your quota".
Zoho Docs web page "Storage details" says 3.45 GB used.
My local Zoho Docs folder (including all synced folders) is ~0.8 GB (total!!).
Deleting files / folders from local folders/web site, including files in the trash folder, does not change the size reported by the icon.
How do I recover the missing 2 - 4 GB quota space?