License codes are either additive or exclusive.
Additive license codes are generally used to increase the number of available licenses or number of client computers or to change the expiration date. Your vendor can tell you exactly what parameters have been changed by the additive license codes given to you.
An exclusive license code completely replaces other licenses, regardless of whether they are additive or exclusive.
Note: Redundant license servers handle additive license codes slightly differently. A redundant license server may service both redundant and non-redundant license codes. A redundant license code that is additive will always override any exclusive or additive non-redundant license codes for the same application feature and version.