The first vertical column shows levels of intererence in the WiFi of the unit, red is not a good sign.

The rows show what the unit in the first column has connected to over Sonosnet and with what signal strength. Again, red is not good.

You should probably be not seeing any music stuttering based on how your snapshot look - the one in red has good connections across. In which case, you can ignore the red. Or, try to fix that if you must by playing with other WiFi devices that are close to it, and see if the red changes to yellow/green, if any are turned off. That should allow you to know which of these to relocate to some distance away. Or the red may be a even a distant microwave oven at work.

But if you are seeing no issues with the music play, you can ignore the red box.

Note that some of this is deprecated, especially as the newer devices either don’t report to this matrix, or simply don’t connect to SonosNet at all. As @Kumar implies, if you’re not having issues, you should safely ignore it.