I don't get it Bolt

Excuse my ignorance but if the timing method for a football guy is from movement/passing a startpoint (0y) to 40y (34m) then what is difference if we get the ET time of bolt to this point (I assume something in the lines of 1.85, 1.02, .97, .36 (guessing here)) 4.20s less reaction time .10s and (what is the leadin time for football (??? .20m)) do we take off 1/2sec off for block clearance time (0.5s) 0.25ish, does this mean he is in the realm of sub 4s for 40y maybe 3.90