What is happening with the staff spacing of the final system here?

[FredGUnn]

I found @benwiggy’s vertical spacing guide helpful for understanding stuff like this too:

Guide to Vertical Justification

I’ve struggled ‘for some time’ getting my head around the Vertical Justification settings. I had set values that worked for me, saved as defaults, but I had no idea what numbers to plug in to get a particular effect. So, I’ve produced the following handy chart, which may be of help to others. Vertical Justification settings.pdf.zip (556 KB)