Subdivision Surface shrinking / not displaying as following UV sphere properly Following eyeball tutorial https://www.youtube.com/watch?v=n0r0UnaIK_Y

When I create a UV sphere and apply subdivision surface it shrinks the sphere slightly. In the tutorial it looks like his subdivided sphere is not shrunk and he can position/edit his sphere to match the reference image precisely.

The difference makes it hard to follow what he is doing. 



Everything seems the same, how do I either make my subdiv modifier behave like his or if this is just to do with the display of the sphere make that the same so I can follow his steps?
Figured it out, I needed to check "Adjust edit cage to modifier result"