No, 555 isn't necessarily your house number, e.g. 2030 East Street, (fictitious address) could be a block of apartment buildings or townhouses and the "house" number is 12A (apartment/townhouse 12, block A). Just fill it in in the way that is most logical, try not to read into it so much.
Some towns are divided into "districts". If this is not relevant to you, then don't put anything there.
dis·trict [ dístrikt ]
area: an area of a town or country, especially one with a distinguishing feature or one that is an administrative division
divide into geopolitical areas: to divide an area into distinct geopolitical or cultural sectors
Synonyms: region, area, locality, quarter, borough, ward, constituency