OSX Update 10.8.3 Bug - decreases graphics ram

I have a 2012 MBP. I installed the OSX update 10.8.3. After that if I click on the apple icon > about this mac, then the video ram has decreased from 512MB to 384MB. I rolled back to 10.8.2 using time machine. and I got 512 graphics ram. I again did the OSX update and the graphics ram dropped down to 384MB.

Has anyone come across this issue?

Thanks,