Buy Halloween Candy for a Range, Not a Crowd You Invented
The first bag goes into the cart because Halloween is coming. The second goes in because the first looks smaller than it did from six feet away. The third is insurance against becoming the dark house at 7:40. By checkout, the household owns 420 pieces of candy and no estimate of how many children will knock.
Halloween candy is a tiny forecasting problem dressed in orange packaging. The household must buy before it knows the visitor count. Rain, school schedules, neighborhood events, apartment access, day of the week, and simple chance can change the evening. Precision is impossible, but an unexplained mountain of candy is not the only alternative.
Use the evidence available, plan a low and high visitor count, decide how many pieces each visitor receives, and make leftovers part of the decision. The result will still be an estimate. It will be an estimate with a reason.
Write down the best count anyone in the household remembers. A tally is better, but an honest range is useful: around 40 visitors, between 70 and 90, fewer than one full bag, or nobody because the building did not allow entry.