They say if you have a 500gb system you can use about 465gb of it but mine says 364gb when...

The 364 is actually normal for Xbox. It's due to system files.

A Typical 500GB hard drive will actually be 465GB after formatting. The Xbox One will however have 3 operating systems. These OS's will be pre-installed on the hard drive. After that I would say it will probably have about 450GB available to the end user.

start with the basics.

hdd manufacturers count 1000 Megabytes to a Gigabyte.

Software is designed and calculate hdd space as 1024 Megabytes in a gigabyte.

500GB when formatted is 465GB

Then you have the system files, xbox 360 system files, cache, updates and reserved storage for screen capture and video capture.

A 500gb isn't going to be 500gb as the first thing, more like 465gb in actual usable space.

Then Elite hits it spot on, you are losing a large slice of that space to the operating system.

500gb doesn't go a long way in this day and age.

I would seriously suggest investing in a USB 3 external hard drive for your console if you aren't the sort to be deleting all the time.

Well its a 500GB hard drive.

After typical format of a 500GB drive, you get 465 real gigabytes

So user available space will probably be between 400-465GB