A Match Up will search through all of the apps and drivers you have installed on your hub and attempt to figure out if there are packages available that match these apps and drivers. This isn't an exact science. The Hubitat Package Manager will show you matches it found and allow you to confirm those that appear to be correct. This will then cause the selected apps and drivers to be monitored for updates. Unfortunately, the package manager has no way to know what version of a previously installed app or driver was installed. You have two options.
You can either tell the package manager to assume that the version you have installed is up to date, or not. If it is set to assume it is up to date, you will not receive update notifications until the next time a new version is available. If it is set to not be up to date, you can immediately perform an Update which will ensure the latest version is installed.