It is my understanding that the boxes to the right of the map are showing you by color what zones are included in your area. The background color of the map is the same as the box checked, in this case, zone 6b. Checking a different box would not change the zone/map unless you changed the location you are looking at.
. If you look at this link, and select your state, it will show you all zones in New Jersey...there are 4 zones in your state: 6a, 6b,7a and 7b. It is quite possible to have areas to your North that may be warmer, or to the South of you that are colder. The zone is determined by a number of factors ....Elevation,proximity to water, (areas North of you that are on the coast can be a warmer zone than you).....and the valley between two mountains would be warmer than the top of the mountain. These areas are called Microclimates. You can have a microclimate in your yard. If you have fence that blocks the north wind and heats up in the sun, that area becomes a microclimate because it is warmer than the other side of the fence. A plant that would freeze and die on one side, may only freeze back and return in the spring. The map link below is the most recent showing the 2012 zone revisions. Some areas have changed zones because the average winter low temperature has increased over the years...concrete, asphalt , steel and brick in cities heat up in the sun and release that heat at night....other considerations like pollution, clouds and even heat from engines can raise the temperature in an area. I hope this helps answer at least some of your questions.
http://planthardiness.ars.usda...
