I'm positive that your tool isn't taking the split memory into account. An important thing to remember is that you haven't got 1 physical block of ram containing all of your computers ram, you have 2 or possibly 3+ blocks which combined provide you with all your memory. To you this is no issue, but when it comes to programming you do write programs specifically tell them to use ram block X.
I'm not a Mac, but go find a better and more professional tool to measure these things.
Also 2750mb RAM used on almost nothing seems extreme to me, might want to look into that. Graphical desktop applications in general are a huge burden performance wise, so might want to cut back on those