I seriously doubt it's a months worth of browsing, lolz.
It's like those tests in which they test how far a car can go on a tank. They set up a perfect surface, perfect conditions, and keep the car steadily going at a steady speed and rpm. Something which would realistically never happen, accelerating once on a full tank.
I mean I guess it's still a lot, but, you know, it's very much rounded up.
Personally my phone would go days, but I can drain it in a matter of hours with active use. (This is like 6 years old though, but had a very large capacity for when it was released)