Window below the main tuning window

Windows_10

There is a rectangular window with a moving red line and a fixed green one below the main tuning window that I don't understand. The red line sort of moves with the line in the main window but not exactly, so what is it for and what do the lines represent?

Thanks

[deleted]

The green line represents the target note (which will be the one you need to reach in order to tune up your instrument), the red line represent the note you are playing at the moment. The idea is that both lines match, this is the indicator that your instrument is tune.

Windows_10

The green line represents the target note (which will be the one you need to reach in order to tune up your instrument), the red line represent the note you are playing at the moment. The idea is that both lines match, this is the indicator that your instrument is tune.

So there are two windows that do the same thing, is the smaller window more sensitive perhaps?