Not so much a misunderstanding as an appliance failure on one of the most important days of the year, but since it involves a large order, it's somewhat relevant. One Christmas, we had friends and family over for Christmas dinner and my Mom was all set for cooking the turkey, but our stove apparently had other ideas. The turkey had sat in there for a couple of hours before the realization set in that the stove had quit. That year, we had to order from Swiss Chalet (a Canadian restauraunt chain) and it was quite a memorable year.
I don't know about US KFC's by my local one has a big storage area behind the counter for ready pieces of chicken and other stuff so they just have to pick them out and arrange the meal. Burgers and such need a bit more time but rarely more than 2-3 minutes. 4 dinners at once is maybe a bit too much for drive thru.. just get your lazy ass inside and don't plug the line while they gather everything up.
I'm not a lazy ass, and it had never been a problem before. Either way, you don't, as a Manager, call out a customer who did nothing more than place an order. It takes them about 3-5 minutes per order. My order was no different. Far be it from me to expect a fish restaurant to have fish readily available.