When Greg was solving this question he didn’t show us how to find the 16th interval nor covered in the previous video so it felt a a step was skipped telling how he found the 16th interval as he totalled the number of minutes could have added a note on how 16 came to be.
Well the assumption is that you know how to compute the median of something like \{a,b,c\}, where we assume a < b < c for brevity’s sake.
In other words, i think you’ve already been taught how to compute the median of a set consisting of 31 elements, so this is just a direct application of that.
Just for confirmation the preceding prepswift lesson does indeed cover that, as evident here:
(Instead of seven numbers, you’re dealing with 31 numbers instead)
Following the logic of the image above, the median of 31 numbers (when arranged in ascending order) will be the 16th number.