On this screen you can see the version number and build date for this version of TuneLab Piano Tuner. The Calibrated sample rate displayed here is the results of your calibration. The nominal sample rate is 22050.000. When you do a calibration, TuneLab determines and stores your device's actual sample rate, to be used to precisely calibrate TuneLab.

The button labelled "Reinstall sample tuning files and historical temperaments" can be used to reinstall the files that came with TuneLab and were installed initially the first time you ran TuneLab. These would be the sample tuning files, the "Average" tuning file, and the pre-packaged historical temperaments. After these files initially were installed, you could have deleted or modified them. If you did that, and you would like to get those files back to their original state, then you can tap on this button. Reinstalling these files will refresh only the files that came with TuneLab. It will not disturb your custom tuning files or any new temperaments that you may have created. So it is a completely safe thing to do, unless you made some changes to the pre-installed files you wish to keep.