Clean Install has used 15GB !?

[LevMac]

Hey guys, wondering if someone can help me out here, just installed Mountain Lion "fresh" off a bootable USB flash drive.
I went through Disk Utility and Erased what was originally on the Macintosh HD, then continued on with the installation of Mountain Lion, but it is showing that 15GB is used ??

Surely this cannot be right, can someone lead me in the right path ?

 

[LevMac]

Can someone please help ??

 

[brand]

Can someone please help ??

8. Bumps. Posts that bring a thread to the top of the New Posts list but add no content to the thread (bumps) are not permitted. This applies not only to posts that say "bump" but to those with the intent to bump, e.g. posts saying "anyone?" or the equivalent. See why and how to avoid bumping.

Nope.