How do I perform a standard erase on MacBook Pro Retina SSD?
You can't perform an erase because you have booted from the SSD.  Hovering over the icon, will tell you why



To erase your SSD, boot from recovery or from a bootable USB then erase.  If you are sending it for repair, just create another admin account and delete your user profile.  It's much easier and just as secure.  The moment you finish deleting your files, they will become unrecoverable