Final Cut Pro X only uses 500MB RAM

Hey,

I tried everything suggested in this thread: How to get FCPX to use all my RAM?

like trashing the preferences, using optimized media, checked my project settings and so on.

However when I try to transcode, render or export, Final Cut uses up to 300% CPU but only about 520MB of RAM.

I am using a late 2011 MacBook Pro 2.8GHz i7 with a 250GB SSD and 16GB of RAM.

So why isn't Final Cut using more RAM?

P.S. I'm editing 1080p 30fps mp4 GoPro files.

Stefan