Huge gap between size of drive and size of all files and directories

Question

I have Windows 10 on laptop with 1TB drive on C: When I run Properties on C: - I get "Used space" equal to almost all 1TB and "Free space" of only 1GB When I run Properties on all files and directories on C: - I get "Size" 329GB and "Size on disk" 331GB All the hidden and system files are set to be visible A few years ago, I installed Microsoft Azure Service Fabric SDK which seems to be responsible, because it created a folder named C:\SFDevCluster\ which eventually showed "Size" 600GB and "Size on disk" 9GB. I uninstalled the SDK and deleted the folder, but the problem with my C: dive remains. The chkdsk.exe does not report any errors on the disk. The Windows Disk Cleanup does not show any space of that size to clean up. Any ideas?