It's not so much the number that will give anything away. It depends on several factors, battle or quiet area, enemy encounter setting in workshop, flight path, weather, etc.. you could have 200 aircraft and not meet any in your mission or run into several during a mission
It is all random, so the number doesn't mean much. When a tweaked version of the weather mod comes out by BB, then air activity will change somewhat and that number will be important to change/adjust depending on the day you fly