Beachgurl,
I can't find anything about an extra 4 days here
http://www.fairtrading.nsw.gov.au/ftw/Tenants_and_home_owners/Renting_a_home/During_a_tenancy/Rent_increases.page
The only thing I can think of is in some areas of law you need to add 5 days for a notice to be deemed served by post...