When additional certificates are issued

Hello, please tell us about summarizes how the data in the case of additional issue the certificate.

For example, issued a certificate to about 100 people (at batch). After that, if the shortage was found and it became necessary to issue additional certificates to 20 people.
Is it better to issue 120 people together with the previously issued 100 people, or to add 20 additional people together?
Or let us know if there are other ways.
If it is the former, do we need to replace it with the already issued blockchain certificate?

I can answer this and your other two questions. Could you send an e-mail with some background info on your project to dev@blockcerts.jp?