I have a new 1 TB WD My Passport hard drive, Model: WDBBEP0010BBk-EESN. I checked the properties of the hard drive when I first plugged it in, the used space was 320 MB, though the total size of the data was 191 MB which is the software that comes with it (of course I show all hidden files and hidden operating system files).
I did a quick format to the drive, but the space is still used (129 MB). I copied some (2.69 GB) of data on the drive and then deleted them, the used space even increased to be (168 MB). I've done quick format on the drive again, the used space returned to be (129 MB), I then copied the same data (size: 2.69 GB, used space: 2.93 GB) then removed it, the used space increased again to be (168 MB). I then copied data to the drive with size 19.6 GB, the used space became 20.2 GB.
I deleted all of that data to make the drive empty again, the used space increased further to be about 300 MB. It seems that the more I add data the more I lose space. Can anyone tell why this is happening?