I might have missed it, but after I got through implementing the preferences, I found I had to make one more change to the EggTimer model in the resetTimer function and take out the line which set the duration to 360.
This tutorial is more than six months old so questions regarding it are no longer supported for the moment. We will update it as soon as possible. Thank you! :]
This was updated on Jun 14, 2021 by @robertomachorro, so reopening comments! :]