about the measurements, in the manual (end of page 6)

[rmacrino]

I am learning and I would appreciate an explanation about the measurements, in the manual (end of page 6) where it says "
The bottom line shows settings and results of measurement and calculation."... thanks a lot

[Ho-Ro]

The meaning of each value is explained at the bottom of page 7.
If you want to learn more you could read about the mathematics of AC voltages in Wikipedia and about THD (Total Harmonic Distortion) and see calculation examplex for a square wave and a distorted sine signal.
If you want to see the magic behind just have a look at the calculation, I spread a lot of comments to guide the reader through the data flow.