CatNap -- how to position the CatWakeUp sprite?

Page 236 of the book describes positioning the catAwake sprite @ CGPoint(x: -30, y: 100).

The commentary describes this: “You set the node’s position to make sure that it will appear exactly over the existing texture.”

Can someone explain how to calculate the values of -30 and 100? I’ve looked at the positioning of the original shared_cat sprite and can’t figure it out, but I’m sure there’s an explanation. I want to understand the calculation so I can do the same with my own shapes in the future.

Thanks.