The “MO Health Scores” section of the document you referenced describes what goes into the leaf and spine calculations, but perhaps this will help:
There’s also some discussion on health scores here:
And I’m not sure you can get to this, but it also sheds some light:
Basically, it states that there is no real need to know how to calculate health scores to use them effectively, but there should be a basic understanding of whether faults should have high, medium, low, or “none” fault levels. Though faults in ACI come with default values, it is possible to change these values to better match your environment.
Hope that helps a bit.