Floor 1056

After being shot through the chest, Bill Potts was taken to Floor 1056 of the Mondasian Colony Ship to be "repaired".

It was the lowest floor on the ship and thus the furthest away from the Black hole that the ship was slowly moving away from. As a result, time on this floor moved at a normal rate compared to Floor 0, where time moved so slowly that it appeared to those on Floor 1056 that there was no movement at all. (TV: World Enough and Time)

Behind the Scenes
The numbers of the floor equate to 12 when added together, a reference to the starring Doctor.