How is the Security Rating is calculated?

Is there a reference as to how the Security Rating of a website scan is calculated?

At some point the Security Rating was an external link to snyk.io. There, the vulnerabilities of a given website scan were listed and explained.

Now, I only see the rating without any further information. The only thing I could find was on the Experiments page under Resilience. But that section doesn’t include all issues. Security Headers are not listed for example.