Which is the dataset that is referred to?

There seems to be an Error in the Course?!
In the 5th Lesson, the plot is meant to illustrate the “dataset introduced in the last lesson”, where all 4 previous lessons used simple arrays of 5 elements as data.
Am I missing something, or is there a big chaos in this Course?
So which is the Dataset that is referred to in the 5th Lesson?

It is referring to the array that is used in the previous lessons calling it as dataset