Details on coverage can be found on the West's Insurance website at http://westinsurance.com/homebrew-home.html. Questions about the coverage should be directed to West's, as they are the experts on this program.
Actually, no details are found there and my request for coverage information from this past weekend has not been responded.
Drew summed it up nicely
Every physical body that is part of the dues paying structure. (e.g. member or each person in a family member) is counted.
Make an honest assessment based on this and you should be good. If you don't have dues a body count is needed, Note that typical attendance at a meeting is 40-60% of membership and will vary by club.