I am very active person in stackexchange, specially with Stackoverflow.
I was at the top as +52543 changes. I am the only one user with this highest changes.
So my question is how stackexchange define changes ?
It is your position change in that particular section of the users. To be simple: Your weekly rank change
You position changed +52543 (you tackled 52543 users) in this weekly session. You can see other users too, they're loosing their position by 1 or 2, and some are gaining their place by 1 or 2 again.