Recovery Calibration: time period where WHOOP learns about you (the user) and sets an educated baseline that's personalized to you.
How does this apply to me?
The first time you record a Sleep on WHOOP, your data is compared against typical Recovery metrics (like Heart Rate Variability (HRV) and Resting Heart Rate (RHR)) based on your age, gender, and fitness level. As time goes on and more of your personal data is stored/measured, your Recovery 'calibrates', and your personalized baseline is used to generate your Recoveries. After 4 consecutive Recoveries, your Recovery is considered to be calibrated, or measured to your own physiology.