The primary reason for the SSL check is to check that your certificate is renewing properly, and isn't about to expire
We check the certificate regularly, and if it is close to expiry (you set the trigger threshold), then we send you a warning
We'll also send you an update when your certificate succesfully renews
We also make simple checks to try to check the validity of your ssl certificates
If we detect an error (wrong host, self signed, untrusted root, incomplete chain) then we'll let you know. We definitely don't check for revoked certificates, and we definitely don't check everythign that could go wrong with your certificate!