Why does my PS3 tell me I've used 14 GB of space when I'm sure I haven't?

I have a ps3 with a 40GB harddrive. I only have two games with saved progresses on there, GH3 and Gran Turismo, I can’t recall exactly how big the saved progresses are but less than 1GB each. I have about 2 CDs worth of music on there and that’s all. I have made 1 internal memory card for PS1 games which is 112KB I think. When I check the memory settings it’s out of 37GB which I understand as 3GB being used to run the system etc, but then it says I have 23GB out of 37GB left, which implies I have used 14. I don’t know how to see a list of exactly everything that is on there but as I said I’m sure I haven’t used 14GB of space.