From: US Midwest
The small number refers to AA value. Resources can buy AA just like units, in fact, they can buy AA up to level 5, while units can only buy it up to level 2.
You must understand that supply for aircraft works differently than supply for ground units. An aircraft MUST be attached to an HQ to receive proper supply(well, almost always). I have noticed that if there is no HQ anywhere near an air unit, it will receive supply from a resource like a ground unit, but only if there is no HQ anywhere near. Maybe this is a bug, or maybe intended, perhaps sPzAbt653 could tell us.
Anyway, it always best to have an aircraft attached to an HQ, if the game thinks that you have not attached it to the best possible HQ, it will highlight the unit in purple.
But then again, what do I know, I can't read code.
I'm a cowboy..
On a steel horse I ride..
I'm wanted.. dead or alive