Size discrepancy between Cobian Reflector and File Explorer (Windows 10)

[Durant]

Hello.
:)

As the subject states, there is a size discrepancy between what file explorer shows was backed up on my external hard drive, and what Cobian Reflector diagnosed it would (and did) back up.

THE SITUATION:
I did an incremental backup.
It was the first backup ever, so CR (Cobian Reflector) did a full backup, as is stated in the documentation.
All went well.
The total of copied data according to CR was 219.93 Gb.
The copied data to my external hard drive, according to Windows 10 file explorer, was 505 Gb of data.

I did 3 different backups as tests that day before doing the real backup, and all results showed this kind of discrepancy in sizes of more than double.

INFORMATION:
My external hard drive is a SanDisk solid state 1Tb drive.
It was empty, formatted to exFAT.
Partial list of task properties in image attachment.
Size discrepancy pictures as attachment.
My back up is of drive C, with the following excluded files:
- Recovery
- (my anti-virus data folder)
- (2 different folders with video games installed)
- Windows
- XBox Games
- $WinREAgent

QUESTIONS:
Why could this be taking place?

Thank you very much for the time given to this post and specially for CR, which is as close to what I need in a backup tool as I could possibly imagine.
Old school style! Yesh.
:D

Durant.

[cobian]

The size of the backup is the size of the source minus the size of the excluded files/folders. Perhaps that is the discrepance?