Dogbreath,
The licensing would be what is called concurrent licensing. This means that you can have 20 people with a certain license, but only the amount that can actually use it at one time is where the limit comes in.
For example you have 6 supervisor licenses, but you have 9 people setup up to use it. If 3 of those people are logged in using it then you would have 3 still available that could use it. After that the remaining 3 people, out of the 9, would not be able to log in until one of the others logged off.
Thanks,
TE