Difference between Available and Used in Info for MacIntosh HD and Space Free and Space Utilised under Activity Monitor, Disk Usage?
I have a MacBook Air 2010, upgraded to OSX Version 10.8.4. When I click the Macintosh HD and then look under Info, it says I have 120.47GB capacity, Available 60.97GB, Used 59.5GB. However when I look under Activity Monitor, Disk Usage it says Space Utilised 92.18GB, Space free: 28.29GB. Questions:
Why the difference?
Which is more important for computer speed?
How to I reduce "Space Utlised" to closer to "Used"? (I've already moved 25GB of the more bulky, less immediate data to external storage from the computer, including emptying IPhoto Trash and the main Trash. The Space Utilised dropped only from 95GB to 92GB--while the Used space dropped from 85GB to 60GB.)
MacBook Air, OS X Mountain Lion (10.8.4), MacBook 2010 version, upgraded to 1