The blue dots on the map represent up to the first 1000 results shown in your property list based on the "Sort by:" drop down (as seen below) that has been defaulted or applied. 

Changing your filter at the top of your list or adding/taking away search criteria will result in new properties being populated, changing the dots displayed on the map. 

To see more dots of properties meeting your filters, keep scrolling down the result list. This will lead to new dots populating on your map allowing you to further prospect.