It's all a guess based on what historical data they have and they prey on people who don't go often or first timers. I don't know if Touring Plans still does it but years ago, they would show their guess and then a day or so after, they would post the "actual". One year, we went during Spring Break expecting high crowds and TP had a 9 for Animal Kingdom. We went to AK and it rained all day creating walk-ons for almost everything. The next day, they reported "actual" was a 9. It made me question their whole model and legitimacy.