Xperia Pro/Neo/V/L :: Internal Storage Space Less Than 320 MB?

I have bought xperia NeoV 4 days ago, I need some clarity on the internal storage space.Like the Internal storage space is said to be 320 MB, but when I have checked in Settings >> Applications >> Manage Applications in downloaded section the system says that internal storage consumed is 279 MB. But when I manually add the space consumed by each applications i get only 126 MB, can I see which folder/application is using 153 MB extra space and is hidden from display?Is the system showing extra space consumed than actual? I have cleared all the cache and history also, even though the phone displays 279 MB consumed. how can I regain that extra space which phone is not displaying.