BTO 13" MBP 500GB, not 512GB?

[JFJetta]

Can anyone answer why my newly arrived 13" MacBook Pro non-TB, which was ordered with 512GB reads that my drive is only 500GB? I'm not talking what's on there for the system, the TOTAL space is 500. 477 available of 498 with everything installed. Thanks!

 

[wlossw]

overprovisioning. some of the drive is left reserved for performance and reliability purposes.

 

[vjobs]

1. 1GB = 1 billion bytes and 1TB = 1 trillion bytes; actual formatted capacity less.

This is what Apple says on their website.