6DW is the Incode, (6) represents a district sector, the last characters identify a group of addresses within the sector, usually about 15. When inserting a space in postcodes there should always be characters in the incode.

6DW is the incode. 6 represents a district sector, while the two alphabetic characters identify a group of addresses within the sector. Postcodes can represent a maximum of 100 addresses, although the average number is 15.