I’ll leave a link to a couple of posts where I explained this in detail:
It’s not a fixed effect, since it follows a curve (diminishing returns) and depends on the power requirement of the item you’re crafting, so it’s really not easy (or possible, really) to make it fit in a tooltip.
The coil would have to predict not only how many other coils are in the machine you’re gonna install it, but also the power cost of the item you’re wanting to craft, before it being installed.
The percentages in the tables I linked work for 0 power cost crafting.
For things that require power, consider the first column to mean “number of coils over the requirement” instead.
