About This Mac -> Storage is wrong? Per Apple->About This Mac->Storage, it says Apps - 276.79GB, yet when I do du -hs via Terminal, I'm getting something else:

alexus@mbp:~ $ sudo du -hcs /Applications/ /Library/
Password:
 22G    /Applications/
 10G    /Library/
 32G    total
alexus@mbp:~ $ 


same goes for Photos (31.79GB), Audio (29.68GB) and Movies (11.3GB):

alexus@mbp:~ $ du -hs Pictures/ Music/ Movies/ Downloads/
5.9G    Pictures/
 29G    Music/
496K    Movies/
 80K    Downloads/
alexus@mbp:~ $ 


I'm confused, how is it counting exactly, or what is it counting)?

alexus@mbp:~ $ df -h
Filesystem      Size   Used  Avail Capacity  iused    ifree %iused  Mounted on
/dev/disk1     465Gi  212Gi  252Gi    46% 55751222 66086376   46%   /
devfs          326Ki  326Ki    0Bi   100%     1128        0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0        0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0        0  100%   /home
alexus@mbp:~ $ du -hcs ~
146G    /Users/alexus
146G    total
alexus@mbp:~ $
The Storage pane will show you information about files matching those categories inclusive of the entire drive, not necessarily only the files stored in those respective locations.

For example, if you downloaded a 5GB movie file, that would be +5gb in the "Videos" category, even though it might reside in ~/Downloads instead of ~/Movies

Source

That being said, your overall usage does not come anywhere close to what the storage is reporting, in terms of the entire drive having less used than you say for the Apps category alone (unless your question was not clear). To reset those values, perform a reindex of Spotlight:

Run the following command from Terminal: sudo mdutil -E /

OR follow instructions below:

Instructions