The idea works on the real world fact that things become less effecient the longer they are opperational such as need for maintanance ect.
The numbers are completey interchangable but say for every 5 asf made the production time of each following asf would be increased by 1 sec
This would in theory prevent a runaway air dominance of winning /losing a large air fight
so that a player who is behind has a greater opportunity to catch up
and that other players who choose to also make t3 air would have a greater ability to effect the outcome of air superiority.