Do you mean 0.4 seconds?
Yeah 0.4 seconds, my bad. But the main point is that the seeker locks on and starts tracking instantly. So the time between that happening and the fins unlocking doesn’t really matter.
I’m not convinced this report is correct. From what you have said, it sounds like the sensor produces a new image every 0.2 - 0.3 seconds.
You have previously argued an IR MAWS should only be triggered by missiles actually targeting the aircraft, not any missile in the vicinity. With the reasoning that the sensor can track the changing angle between the missile and the aircraft, and determine whether it is flying towards the aircraft. So by that logic the MAWS would need several images of the missile before it can determine the trajectory and decided whether to alert the pilot. So depending on the actual refresh rate and the number of images required you probably are looking at closer to 1 second (or maybe even a little over) between launch and MAWS alert.