Connect your Oura Ring: your Level 2 score is recomputed every morning from your real sleep, heart-rate, activity and readiness data, on a 7-day rolling average. Any other wearable: enter your metrics manually.
A score you type can only go up. A score your ring writes can go down. That is the point. A connected score can go down as well as up; it never drops below your Level 1 score.