Rosa,
The "number of users" is meant for just that--straight user count (what it's doing).

If you want a user count + increment based on computers assigned, that's certainly possible but not at all easy. Furthermore, your question regarding computer type further complicates things, as you note.

If you have ServiceNow's Discovery, you would be able to check the Chassis type of the workstation (it's one of the attributes we find), but otherwise it's next to impossible.

If you need help implementing these new count types, I have a good deal of experience doing so--I rebuilt the Aspen software license engine do do similar things. Alas, the Berlin count engine is all different, or I'd be able to help you much more.