I accidentally entered the wrong serial number, how can I correct this?

Mac v5: Edit the UserInfoV5.xml file in the Macintosh HD > Users > (user) > Library > Application Support > Synergy Software > KaleidaGraph5.0 folder.

Windows v5: Edit the UserInfoV5.xml file in the Users/(admin user)/AppData/Local/Synergy Software/KaleidaGraph5.0 directory. This is a hidden directory under Windows.