Does anyone really know how "MUL+ADD" works?

[Halstrom]

All I really want is a Multiplier, but instead we have MUL+ADD which I assume means Multiply X by Y then Add Y to the result?

[AWP3RATOR]

I looked.... can't find any actual documentation on that particular setting.  From what I gather, it's what you assume it is.  Take the base stat and multiply it, then add.  Though in this screenshot, they are using both.  Looks like the ADD tag is used on keywords here, whereas SET is a true/false and a ref setting.  The stability, sights, etc. are using the MUL+ADD

 

https://www.creationkit.com/fallout4/index.php?title=Object_Mod

 

[Halstrom]

Yeah but how the hell do I divide 10 by 5, MUT+ADD setting of -0.2 gets a result of 1.8? This math makes my head hurt