@ivo, no, it means that the first time you issued a certificate it was validated and this validated authorization will be valid for 30 days. If you renew your cert during those 30 days there is no need to revalidate you domain but it doesn’t extend the validated authorization. if you try to renew the cert after the 30 days it will need to be revalidated and your domains will get a new lifetime validation of 30 days… and so on.
Don’t know if I explained it very well 
Cheers,
sahsanu