iCloud Drive using too much storage on PC

I’ve recently upgraded to 2TB of iCloud so I can take advantage of uploading files to to iCloud Drive so I can download to tablets and laptops when required.

I have a Windows 10 laptop, 2 iPads, & an iPhone.

I’ve been dragging ebooks into the iCloud Drive folder on my laptop, then clicking ‘free up space’, so the files are in the cloud only, and not using space in my laptop.

Unfortunately, my laptop hard-drive is now nearly full, and I can’t understand why. The loss of storage space must be coming from iCloud Drive, because I’ve not downloaded anything else.

Before I started using iCloud Drive I had 150gb of free space, now I have less than 10gb.

All of my uploaded files have either the ‘cloud’ symbol, or the ‘syncing’ symbol next to them.

How come, if all my uploaded files are supposed to stored in the cloud, my c-drive is nearly full?

How do I remedy this?

If this is the extent of iCloud’s powers I may have to stop using it, and go back to Google Drive.