How is the riskAssessment overall confidence evaluated

I have toggled on the “Enable Adaptive MFA Risk assessment” switch in the " Multi-factor Authentication" section of my tenancy. As a result, I have started getting the riskAssessment object in my logs. I notice that the riskAssessment object has an overall confidence value, which seems to be determined by the confidence values of the four Assessor (NewDevice, ImpossibleTravel, UntrustedIP and PhoneNumber). I would like to know how Auth0 determines the overall confidence. I have tried looking through the data but I could not arrive at a formula that will satisfy all the data points.