the odd values are a mistake I did when I translated the kata. It should be corrected now (reset the trainer/refresh the page if it is still persisting)

Hint: n>=6 and look at examples values

These are more ESL problems than math or programming problems. Really wish a native speaker would go through and make all of these less ambiguous.

The kata clearly says "...in such a way that the sum of all the waiting times of the customers..." and "..., return the minimum total waiting time.". So, you don't count only the waiting time of the last customer but the sum of all customers. And that's exactly the point of this kata.