Short summary of "fuzzy logic" is that a bit can take any value between 0 and 1 depending on some "weight" function. Say, 1 elevator is on floor 14, 1 on 15, someone on floor 20 calls an elevator, both get a "call bit" but for the one further from the "target floor" the further one will have the "1" weaker, so the closer one will come. Or, 3 people call an elevator at once, 2 on different floors below, 1 above, so the "direction" bit of going "down" may be stronger than going "up", unless there's just one floor to go up, and more than 10 down etc... - each "parameter" has a weight value, they all add up and depending on the result decision is made.
Usually the algorithm will include a lot of factors though - like usage of parts (so they all get used up at about equal pace so all the elevators should be used about the same amount of time), amount of requests, probably some foreseen "scenarios" and "predictions" (say, weight sensor tells a cabin is nearing its max capacity, so it doesn't stop to pick more passengers, other lifts are sent there instead), estimations of cost and time to achieve given task and many more.