A "--" in the district column means, that the town is a district-free town, i.e. it is by itself a district.
... and the average family size is 2.81. In the village the population is spread out with 20.5% under the age of 18, 6.1% from 18 to 24, 24.6% from 25 to 44, 28.2% from 45 to ...