If I go to About This Mac and click on the Storage tab, it tells me that I have 500 GB of Flash Storage and that 15.49 GB of 399.57 GB is free.
It will also tell me that 226 GB is for System, 130 GB is for Documents, and 25.8 GB is for Apps.
If I do: sudo du -hx -d 0 /*
Tools like OmniDiskSweeper or Disk Inventory X will report the same basic information. They will generally account for the space that the Storage tab says is being used by Documents and Applications, but I cannot seem to figure out where the 226 GB of files are that the "System" part is using. I had this situation come up once before and rebooting the machine cleared out the used space and I got a couple hundred GB back. I could do that again, but I would like to be able to track down what these files are.