You have set up sharing or reconfigured it as far as the OS thinks six times, which allows you to see the name of your Mac in case there is another networked computer with the same name, hence your computer name plus "-6 local".Why are the names different? Where did the -6 come from?
Probably from tradition, just as e-mail addresses used to be all lowercase.Also why are shared computer name in Computer drop down all in lower case letters?