Yes, it's 64-bit. The system does say that I have 4.00 GB of RAM installed, but 2.99 GB usable is in brackets.
All of my machines say they have less usable RAM than they have installed. For example, this machine has 16GB RAM but only 15.9 usable.
In your case the difference is negligible, but @PEllis has just over a 1GB of RAM that can't be used.
The cause is most likely due to integrated graphics stealing... err... umm... "sharing" a large chunk of your system RAM for graphics processing.