*POKE POKE*That is to say,
it's the size of the object (m) x 1000 ÷ the number of mils = the distance (m) to target.
The size of this car is 5m, therefore it's
5 * 1000 / 3 = 1666m"Mil" is an abbreviation for milliradian, a dimensionless unit of angle. The dots on the scope crosshairs as depicted on the blackboard are spaced at one mil intervals.
360 degrees equates to 2*pi radians. Using the equation s = rθ (where the arc length 's' at radius 'r' subtends angle 'θ' measured in radians), if any two values are known the third can be calculated.
Milliradians (0.001 radian) are more convenient for use in gunnery and other tactical applications, and introduce a factor of 1000 into the calculation, as shown in the example in the comic.