windows - Task Manager and memory usage

I'm a little bit confused about Task Manager and usage memory.

Is the sum of all memory processes equal to the physical memory used?

This is a picture of my Task Manager ordered by memory usage high to low:

This is a screenshot of the physical memory used at the same time:

However, the sum of all the memory processes is less than the ~11 GB shown in the second picture.

Which is the true usage?

The OS is Windows Server 2003 Enterprise Edition 64-bit (running on a virtual machine with four CPUs and 24GB RAM)