Receiving my order late

Got to McDonalds and ordered 6 Nuggets and Mini cup corn. I made my order at exactly 10:49. Customers who ordered Foldovers, Big Macs that order after me had received their orders. As they saw that I was getting annoyed they kept on telling me that my order of 2 simple things will be ready. I got my order at exactly 11:09. Can someone explain how 6 nuggets and corn can take 20mins when orders are as per slips. I'm extremely disappointed with the service I got because I love McDonalds but after this long wait, I'm uncertain of that.