You have these activation options because you are allowed to activate two versions of Sage 50 on the same computer and you have already activated one.
Upgrade or update your current version - Select this if you are updating your activation because you have purchased more licenses or you want to change your current version of Sage 50 to a different version.
Note: If you are updating or upgrading Sage 50 on a network, you must select this option and enter the activation information on each computer that has Sage 50 installed.