@DeaconHarry16: The green trace is a zoomed-in and re-centered version of the portion of the white trace surrounding the frequency of interest (464.575 here).
The white trace is centered where the SDR tuner is actually centered (apparently 465.175 here) and zoomed to display the full bandwidth of the SDR (2.4 MHz). The green trace is centered on the frequency of interest (464.575 here) and zoomed in so you can see the characteristics of that particular signal.
In case the DSD+ folks are reading: It would be nice to have an option to display two separate windows instead. I would rarely need to see the green trace more than about 3x the signal bandwidth (~25 kHz in this example), so the window could be much narrower, even at the zoom shown (about 16:1 – 150 kHz total displayed in the example).
The gray area in the center shows the selected bandwidth (7.8 kHz in this example) and is related to the green trace. The white trace has a similar band shown around the 464.575 peak, but it's hard to see because it is 1/16th the width of the center one. I think the light- vs. darker-gray shows the -6 dB bandwidth vs. about the -20 dB bandwidth – the ratio between them being controlled by the -t (standard/tight rolloff) option.
The frequency tooltip that follows the cursor apparently applies to the white trace's scale.
An alternative to two windows would be to show two horizontal scales – one across the bottom in green for the green trace (464.500–464.650 range) and another across the top for the white trace (463.975–466.375). The tooltip could also have a green (464.575) and white (465.175) value.
