Answer: Fifteenths are shown in the example model because the denominator of your answer is also 15.
Explanation:
Like what I'm trying to say is is that this is common sense and also I don't know why your math book would want you to solve this but, since the answer is 6/15 then it wouldn't make sense for your answer table to have 16 spaces instead of 15. Like common sense, although I can get why you're confused.