It gave me back 15GB! 
Note the word "temporary" for the solution: having a disk this full will make it slower. I set it to 2% too on my own disks, but it's better not to fill it all the time.Thank you very much for the help. After I got back the 15GB, I went to my Windows 11 installation and shrunk that volume to get additional space of 300GB (using Disk Management in W11). Then after a lot of head scratching on how to append this to root partition, someone on AskUbuntu had suggested using Gparted from a bootable USB. This helped tremendously. It allowed me to add the 300GB to the root partition and now I have 800GB of space.
I ran Bicoincore last night and voila, I have all the blocks downloaded and syncd.
Thank you everyone for your valuable assistance