The 0.4 is in seconds. I ran a little test on the TEC carrier.
The carrier starts to build 1 bomber that cost 30 AM to build. After starting on 1 bomber the carrier AM goes from 400 to 370. It builds the bomber in 27.5 seconds while regenerating AM at 0.4 seconds. After building the bomber it has 381 AM. Then starts the second bomber so AM goes to 351.
So it looks like you can tweak the AM regeneration rate, build rate, AM cost, or even decay rate of the bombers after the carrier dies. Most values are in seconds.
Thanks for the Karma!!