thanks for your post. In order to do 16-8 please cancel your current fasting week and choose 16-8 (one of our standard plans).
If you do't like the fasting times you can move them.
In the current version of the app, you can move the fasting times by pressing the "move fasting periods" buttons at the start of a week or even during the week. You can also enter your meal times so that the app can adjust your times better automatically.