Windows 10 reporting wrong hard disk free space

I have an external hard disk, and for some reason, it is reporting wrong free space.

In Windows Explorer, it is showing the used space is 378 GB.

I tried ruing chkdsk H: /f /r, it seems to report the same usage as Windows Explorer, and it says that there is no problem.

But when I tried selecting all the files inside this drive, it is showing much lesser usage.

I've already set the setting to show all hidden files and folders, also show the protected OS files, but it still caot find about those missing files. And the difference is huge (282 GB). I've already cleaned the Recycle bin as well.

What I am missing here and how do I identify those missing spaces?