Don’t be too concerned about that funny looking function in the previous step, it is quite advanced programming. Essentially, the content body will invoke the custom function earliest-of-dates, pass it your repeating list, and then get back the earliest of all the dates that happen to be present in that repeating list.
Tip: the “Custom functions” is hidden by default. I just upgraded your rights so that you can see access it; you may have to refresh your browser page.