0.68 may be an important number to an engineer. Or it may be 0.67, or 0.69, or 0.70. Why are these numbers, bunched up in this area of the number line important to engineers. It comes down to one word: pace.
Engineers, moreso ones that are in the field frequently, sometimes have to measure distances by pacing. The pace is simply how far one goes with each step is taken, or the pace length. 0.68 is a typical distance, in meters, that an engineer may take in a pace, so that if that engineer were to pace off a field and take 88 paces, then the length of the field is approximately 88 x 0.68 = 59.84 meters, or about 60 meters. Sure, the pace may vary due to slope, wind, slickness of the surface, amount of clothing, etc., but many engineers know their pace length and will use it if ever forced into a situation when a distance is needed and no good measuring device is handy. Fortunately, the pace is always handy (which is ironic considering one uses the foot).

When you see an engineer seemingly walking along and it looks like he is counting, please do not ask what he is doing, nor ask him the time, or how far it is to Albuquerque, or anything else that will take his mind off the task. Let him pace and allow him the joy of measuring a long distance without the use of a tape measure or wheel or GPS device.