I have read similar queries and none have been answered very satisfactorily.
- I have about 400Gb in Dropbox
- I made about 300Gb Online Only
- The free space in my imac has NOT, repeat NOT, changed
- If I look at a file it says Size 1.2Gb (8k on disk) so it has been put to the cloud
BUT BUT BUT, if my iMac does not recognise this free space, why am I going through the inconvenience of making files online only when, as far as the iMac is concerned, there is no additional space.
This is my Dropbox folder:

At least 200G of additional space should be free since I online'd most of the folders.
This is the HDD. It still shows the same amount of free space as it did before I online'd the folders (and the purgeable space has barely changed so it's not that).

If Dropbox cannot inform the OS that there is an additional 200Gb of free space, then this functionality is totally useless.
How do I get Dropbox, to inform the OS that the space by making files online only is now available for me to use.
Thanks,
Kevin