Chandrahasa,
If you're talking fixed licenses the answer is easy: the numbers of people who will access QM!
However, I will assume you're probably talking about Floating or Token licenses. Floating license behavior changed slightly in the soon to be released 4.0.5 release of CLM so I will speak to that as opposed to the "legacy" behavior.
In QM viewing or editing most data will "checkout" a license. At that point the clock starts ticking for how long the license will be checked out, a default of 60 minutes and a minimum of 30 minutes. Subsequent read/write operations performed by the user will reset the clock.
So how many floating licenses turns into a discussion of:
1) total number of people logging into QM
2) their usage patterns - do they log in, print something, then log out for 3 hrs, or are they active?
3) their geographical breakdown / working hours - if I work opposite hours of another user, we can effectively "share" a floating license.

Hope this helps.