Your username and the name you add in File > User Preferences may differ slightly and serve different purposes. You will notice that if you change your name in User Preferences, this will not change your username in the login screen. This is because your username is set when your user is created and cannot be adjusted without the use of execute commands.
We recommend only updating your username when absolutely necessary (e.g. maiden / married name, incorrect spelling) due to the number of records that it affects in Genie.