Upgraded memory but it says 3.75 in Activity Monitor

[cjscribe]

I just upgraded the RAM on my macbook from 2GB to 4GB. But when I check the activity monitor, it says that I only have 3.75 GB. Is this right?
When I had only 2GB of memory, the activity monitor also said I had 1.75 GB.
Where did the other .25 of memory go?

 

[aristobrat]

On-board graphics?

 

[Surely]

^^^ This. The graphics card uses 256 MB.

 

[sammich]

The 9400M graphics card uses shared memory (256MB, or 0.25GB) from the computers RAM for operation. That is the portion missing.