That means that it has arrived at the military post office stateside. It is then handled by military transport and personnel and can't be tracked that I know  of.
Current time from Alabama to Afghanistan is 3 weeks.

Tracking stops at New York or New Jersey something like that. Like the previous poster stated I lived on the east coast and things took 10-14 days to get to Bagram. FOBs a bit more time due to sorting.

Normally its around two weeks from Ohio to Kabul. Have actually got packages in eight days, but that's not the norm.

I've had packages in 4 days from Indiana to Kandahar before... and IIRC, it depends on the destination as far as when it leaves USPS custody and ends up in MPS custody. I believe for Kandahar the packages stayed in USPS custody with full tracking and everything until they hit Kandahar then they were turned over to the MPS that your mail routed through. IE, we could accurately track packages to Kandahar and then they would go "off grid" and typically would arrive within a day or 2 from that point.