User-sessions are allowed via license-granule 1200, NAS-sessions via granule 1420(?).
So - common users and NAS'es are not mixed up in the license.
However - in the Database Information window you see "Licensed Sessions"; and this field does show max common sessions + NAS sessions!
I guess that your license permits 3 common sessions + 2 NAS'es. And your Database Information shows "Licensed Sessions" = 5.
Only clarifying: It is not possible to "use" NAS-sessions for a common sessions.