Can the screen 2nd column ,be explained please

Hi
I refer to a typical audacity screen, the vertical second column has 1.0, 0.5 , 0.00 , 0.5 and 1.0 - what are these actually indicating ?

It’s called the Vertical Scale.

If you go to the Manual’s front page image and click on thet part of the image it will take you to this relevant page:

https://manual.audacityteam.org/man/audio_tracks.html#scale

WC

Thanks for that. It would be good to see it though have some relevance to voltage, rather than a made up scale of lower than 1.0,
as it is at odds with it being described as a RMS value - usually associated where voltage is described.

If not, some means of converting its made up scale to RMS voltage would be of huge help.

It does have relevance to voltage. It is directly proportional. If you calibrate your system so that you know what voltage into the ADC is required for full-scale output, then you can calculate the voltage from the waveform.