When exporting the data, you receive the complete list of subscribers to this list. You will have to make a filter according to your needs. For example, to have the real number of active subscribers, you have to take into account the OPTOUTDATE_WITH_TIME:( Blank = subscribed and With a Date = unsubscribed) and EMAIL_USERS columns (True = active / False = inactive).
Other useful definitions:
DATECREATED_WITH_TIME: date of creation of the subscriber
DATEMODIFIED_WITH_TIME: date of last modification of this subscriber's profile
DATEOFINVALIDATION_WITH_TIME: Blank = Active / Date = Bounced
OPTOUTDATE_WITH_TIME: Blank = registered / Date = unsubscribed
EMAIL_USERS : True = active / False = inactive
ACTIVE: True = active / False = inactive