Here is the space comparison:
|Commad: df -lk||Used(Kilobytes in 1024-blocks)|
It is a surprise that I got more space back after the update. Not sure what caused the gain? I did clean my trash before the update. After the update date, my trash was empty. I went to Finder to duplicate a file and then delete the file. As a result, I could clean my trash again. I did realize that 5 items were securely removed (even one pdf file I deleted). I don't understand that what were other 4 items come from? Maybe I should post this question to SupperUser.com.