The current tuning file label shows the name of the current tuning, if the current tuning has been given a name. When you are not saving the current tuning in a tuning file, but just using it for tuning, this field will be blank. Tunings can be saved and loaded from the Settings page. The benefit of saving a custom tuning is that a record is stored for the inharmonicity measurements and other settings that went into the current tuning. Therefore when you are tuning this same piano some time later, or when you tune a similar piano, you can skip the initial inharmonicity measurement and setup steps and go directly to tuning.