For months now, many of my subscription items are shipping in separate packages. For example my August's sub of 2 APs shipped as 2 separate packages. I get my parcels delivered directly to a post office, so I prefer to reduce the number of times that I need to make the 30 minute drive.
I'm in Australia, so I guessing the Paizo shipping algorithm is calculating that it's cheaper to send them as separate packages.
I did a test, added the same APs to my Cart and then proceeded to checkout. And yes, if they are sent separately, it will cost $10.90 using "Standard Postal Delivery" while it will cost $13.44 for "Mail Innovations International".
Went to My Account.. My Subscriptions and noticed that the "Shipping Method for Subscriptions" was set to "Cheapest Possible" I have now changed it to "Mail Innovations International" so hopefully from now on, just one package per month.
Thought I would share in case others are having the same issue and also to confirm that changing to "Mail Innovations International" will result in one package per month as I would hate to pay extra and still get 2 packages.