Effect of percentages on the right during game dev? (Example: World Design at 90%)

If I’ve got a lot of engine add-ons on the right hand side of the screen, I noticed that as I move the slider down, a percentage starts appearing on the categories on the right. I can make the percentage go away by moving the slider up or by removing engine add-ons.

So I guess this is somehow simulating not putting enough emphasis into, say, World Design, when you’ve got a lot of different technologies in your engine. But what is the actual effect of having a component at 90%? 50%?

Answered here.