Disk storage graphic and usage amount inconsistent?
Blame Spotlight. About this Mac relys on Spotlight's data, and it's clearly screwed up here. You can fix this by forcing Spotlight to reindex your hard drive. Goto System Preferences &gt; Spotlight &gt; Privacy tab. Then add Macintosh HD into the list, then remove it. Spotlight should start reindexing your hard drive. (You can test this by pressing CMD Space and entering an equation. It should say indexing).

(Oh, and this is a duplicate of this Finder and About this mac shows different free space sizes?)