Came here to mention this too. It seems to adjust octaves for you automatically, but that's not at all clear... and I really don't see why it's necessary either.
Thanks for mentioning it! I really struggled with this octaves decision, and wrote about it here: https://news.ycombinator.com/item?id=38410228
However, starting to also think that maybe I should just write a note on the page explaining what it's doing, lol.