[Norfleet]

That is the province's number. All provinces in the game have a number. Even when the province's name is not visible, because you have nobody nearby to see its name, you can still identify a specific province by number.

You can also goto a specific province, by number, using the "#" key (SHIFT-3). Then just enter the number, and that province will be selected and zoomed to.

This number does not indicate anything, it merely serves to identify the province, as it is possible for provinces to have identical names, as the names are randomly generated: it also gives you a method for referring to provinces across games on the same map: Names of provinces are random, but the numbers are always the same.

These numbers are also of use if you are modding .map files to create scenarios, as the provinces are referred to by number in said files.