The first screen snapshot below shows the text for the Bernal Sphere item in the vault.  Note that it says "adds +1 to its usable tiles."

The second screen shot shows that the core world that I am about to apply the Bernal Sphere to is a class 36 planet meaning it has 36 usable tiles.

The third screen snapshot shows that, after applying the Bernal Sphere item that should add 1 usable tile, the planet is now a class 39 planet meaning that 3 usable tiles were added.

I recommend that the text be modified to say "Adds +3 to its usable tiles.".