Not at all, Im saying it would get to 124mph a lot quicker, but that would happen roughly 0.9sec before the finish line so the car would have to be accelerating for longer before it reaches the quarter mile line and therefor be going faster.
As a result of crossing the line at a faster speed, the quarter mile time is going to be quicker...

It wouldnt happen .9 seconds before the line (based on a zero speed for gear change as you are doing)

You would get to 124 in .9 seconds less time.

The difference in distance taken though would .45 seconds multiplied by the speed of the first gear change and .45 seconds multiplied by the speed of the second gearchange.
So if the average gearchange MPH for those two was say 60mph, you would get to 124mph now .4 seconds or so before the finnish line as the distance would only take you that long to crossed based on speeds of 124mph+