I found this info, but it doesn't elaborate much:
"To be counted as a member an individual must have a name, contact details, have contributed $50 to the club and received a membership pack. The official counts also include multiple memberships held by an individual. Pet memberships are not counted but the AFL confirmed babies and toddlers are included."
The $50 Essendon membership doesnt include match access, so interstate and o/s would be counted I suppose. They damn well should be!