The longjumps distance is added by 32 because of the bounding box.
It also depends on how you define a longjump distance. Currently GOKZ attempts to calculate distance from A to C, resulting in 218.79 units (+-0.01)
Worth noting that in reality you are never at that C position. So assuming there is a trigger at C and no trigger at D, you won't touch the trigger.
TL;DR edit: If you want to calculate the distance covered while being considered "in air", go for 217.546875. (95 air ticks)
218.792736 is the real number you should go for.
Proof: You can get the time in the air by solving the trajectory equation
1/2 * gt^2 + vt + c = 0, then multiply
t by your horizontal velocity (250).
g is the gravity,
v is jump impulse value,
c is offset (0 in this case)
g = - sv_gravity = -800
v = sv_jump_impulse - 0.5 * sv_gravity / tickrate = 301.993377 - 0.5 * 800 / 128 = 298.868377
because c = 0, we can simplify
1/2 * gt^2 + bt +c = 0 to
1/2 * gt + b = 0
t = -2b / g = -2 * 298.868377 / -800 ~= 0.747170943
Multiply by 250 and you get ~ 186.792736, then add 32 units of hull size to get the LJ distance.