Here's the cadence (give or take a couple days in each case, depeding on the month) :
Sep 1: October issue ships
Sep 15: Deadline for November subscriptions
Oct 1: November issue ships
Oct 15: Deadline for December subscriptions
Nov 1: December issue ships
So, if you subscribed on the 16th of September, you missed the November issue. Your first issue ends up being December. That ships the first of November, Bulk Rate. You get it around the 10th. Thus, it can take 7 weeks.
On the other hand, had you subscribed on the 15th of September, your first issue (November) would be in your hands in about 3 weeks.
Hope that helps-