Calories are the sources of energy in the body of the human being. These sources of energy are used by the humans to do their day to day activities. Amount of calories that a person should take in a day depends upon various factors. The basic factor to consider while taking calories is to see either the person is a male or female. Calorie recommendations are different in males and females. Secondly it depends upon if you want to lose weight, maintain weight or gain weight. Calorie intake would be different in these separate scenarios. Also it depends upon the level of activity you do. It also depends upon the age of the person. In older age, calorie requirements may drop as compared to that in the young and middle age.
The best answer for this question would be to talk to the cashier, in situations like these the customer is always right and knows exactly what they want, and if that doesn't work out ask the manager so he can get the correct coffee he wishes for.