Send notifications to users with compromised credentials - how often are emails sent? At login or as detected?

“Enable the Send notifications to users with compromised credentials toggle to send an email to a user when Auth0 detects their credentials may have been compromised.”

When does Auth0 check for compromised credentials? Are they only checked at the times they can be blocked (block compromised credentials for new accounts, block compromised user accounts during login, block compromised credentials used for password reset) or does Auth0 check daily/monthly/some interval outside of when those 3 block scenarios are triggered.