How to adjust sleep goal?

I recently got the Forerunner 265, and I'm having trouble adjusting what my "ideal" number of hours of sleep is - the sleep coach seems stuck on the 8 hours. 

It's been known in scientific literature for a while now that 8 hours was an incorrect data point (it was collected from one very small subset of American males), and that sleep needs vary across the population.

Does the goal auto adjust over time, and it's not something I can manually edit?