Invalid volume free block count
I've run the disk utility verify disk several times and come up with an error (post title) indicating I have a corrupt HD and need to repair. I've rebooted with command R and run disk utility to repair the disk and it says everything is fine. Reboot to normal mode and verify continues to show the error.
Other info says the file system exit code is 8.
Any suggestions whether this is serious?
MacBook Pro (Retina, Mid 2012), OS X Mountain Lion (10.8.2)