This may explain the situation a bit better.
MCG
UPGRADE INFORMATION
Due to the anticipated high demand for reserved seating by AFL Members, a decision has been made to upgrade the following matches during March and April of the 2011 Toyota AFL Premiership Season, to 'Reserve on Demand' matches (click here for 'Reserve on Demand' description):
» Round 1: Carlton v Richmond
» Round 1: Geelong Cats v St Kilda
» Round 3: Collingwood v Carlton
» Round 4: Richmond v Collingwood
» Round 4: Carlton v Essendon
The following match during March and April of the 2011 Toyota AFL Premiership Season is a 'Reserved Seat Ticket Event' (click here for 'Reserve Seat Ticket Event' description):
http://www.aflmembership.com.au/reserved%20seat%20ticket%20events/tabid/16440/default.aspx» Round 5 - Essendon v Collingwood
All other matches scheduled at the MCG in March and April are classified as 'Walk Up'.
http://www.aflmembership.com.au/home/newsarticle/tabid/13892/newsid/108739/default.aspx