[Pushed +3] Not all color negative film pushes 3 stops too well but Cinestill 800T is one that is designed to do so.

Cinestill 800T pushed 3 stops to 6400 1

Example of Pushing Film 3 Stops

The pushing or pulling process involves shooting and developing film at a different ISO then what the film is rated for. Let’s say you want to push your 400 ISO film 1 stop (+1), set your camera to 800 ISO and shoot/meter the whole roll as 800 ISO. When the roll is finished, clearly mark the speed on the film canister. Marking the canisters is for your reference in completing the order form and letting the photo lab know how to adjust development time.
Read about Everything you need to know about Shooting and Developing Pushed or Pulled Film