@Wujo ,
I’m really sorry that I missed seeing this a few months ago but it looks like you figured it all out since both of your interpretations are correct. I have taken your advice and added a note to the component description that positive values are helpful and negative values are harmful:
If you find any other issues in the component descriptions or the latest sample files, let me know and I will fix them.
The reason why the values are slightly different than Legacy is because of the reason I described here:
Essentially, the new radiation components are a little more accurate in the way that they try to account for ground-reflected solar energy.