Stay in Your Lane

So there is this new guy at work and for the past few months , he's been just an incredible douche canoe.
I have been working on a project for a couple years now and it's been generating pretty good figures and I gave my estimated figures for this month.
He messages me today and says "you sure it's going to generate that much? I think its going to be lower"
Who the fxck asked you? This isn't his job, why is he trying to track my departments figures?
I talked it over with my colleague later, at least I'm not alone in my general feeling that somebody is steering out of their lane.