Copied files on new WD drive, size and size on disk are different

[tkmops]

Why does my new WD external 4TB drive, after copying some files to it, show size:45.3GB, and size on disk:103GB?

The drive that the files were copied from show size:45.3GB, and size on disk:45.5GB.

I've called WD tech support, they have no idea of why that is.

I've used many WD external drives over the years, this is the first time this has happened.

Anyone know?

Win 7

 

[jumanji]

Look into this for an explanation What's The Difference Between Size And Size On Disk In Windows Folder Properties

https://www.howtogeek.com/136078/what-should-i-set-the-allocation-unit-size-to-when-formatting/