JOIN optimizes your schedule based on soreness, time availability, and overall training balance. If it’s better to take a rest day this may lower the number of running workouts suggested. In your profile, you are setting the preferred and therefore maximum number of running sessions.
But JOIN will always suggest the best combination possible based on your training data and availability. The better you get and the more training volume you can handle, the easier it will be to reach this preferred number of runs.