usb disk 64gb only shows 58.59gb

I have an unformatted usb stick Kingston Datatraveler Ultimate 3.0 G3 64 GB.

When I clean out the disk and I am about to partition and format it, it lists as 58.59GB and in properties it lists as only 60000MB.

I know that for disk manufactorers 64GB stands for 64×10⁹ bytes. And that for Microsoft Windows it is for 64×2³⁰ bytes.

But still I expect to see my 64GB drive listed as 64×10⁹/2³⁰≈59.60GB in stead of 58.59GB. Where is this discerpancy coming from?