Wizard of Alice:
I live at 10123 Viennarose Avenue. Why don't I live at #1 Viennarose Avenue? Why do I have to be #10123? There probably aren't 10,123 homes in all of San Diego, let alone on my street.
-- Ray "I wanna be #1" Vance, the net
Why doesn't every new street begin with house number one? Let's put it this way, if you live on some dinky cul-de-sac buried deep in a housing development and you need a fire engine or an ambulance, you want your house to be a findable as possible. To that end, house numbers in cities, developments, or other defined areas are assigned on a grid system. For example, if you're looking for the 4000 block of Fairmount and you know your street numbers, you'll know that's the first block north of University Avenue. In that area, all houses in the first blocks north of University are in the 4000s.
Anyway, in your Viennarose nabe, the 100 blocks for east-west roads begin at the ocean and get higher as you move east. For north-south roads, the 100 blocks begin on the south side of Otay Valley Road, and the numbers increase as they approach the border. It doesn't matter that your street doesn't run all the way to the ocean or to Otay Valley Road. Your little block happens to fall at the 10100 point on the big grid, so you're assigned a big number.