As you can see, the above two Anchor Point Expressions have very similar code. They both Center Anchor point, then by using extra Sliders, we can Offset it. This allows us to offset Text, to make sure it is visible under all the other Circle Layers. And it allows us to Offset whole shape, to perfectly create Venn Diagram.
Make sure to set up Sliders, so you can control this easily, instead of having to modify the code by hand.
Finally, Rotation Expression simply assigns a degree of rotation per each Composition. It is dependant on the Number of Layers inside that Composition. This way, we can have 3, 5, 21 or more Main Circle comps, and all of them will be spaced out perfectly around 360 degrees.