On the home page of your account you'll find several stats in regard to recent activity. One of the reports you'll find is the Active Users by Postal Code in the last month report. It'll look something like this:
Note: If within your account's details a state has been designated in the address, you will be shown that state's map rather than the entire map as shown above.
There are two main aspects to this report, how many zip codes with at least one active user within a given area, and how many users have entered from a given zip code.
For example, the 2K near Chicago shown above is not 2K active users within that area, but rather the amount of zip codes that users have entered from in that area.
If you continue zooming in, you'll be able to see that eventually a dot on the map will not contain a number, and you can now view the specific number users that have entered from that zip code. In the below example you can see that the dot next to Kanakee fits that criteria:
Once clicked on, that dot will now show the specific location and zip code, as well the amount of users that have entered from that zip code.
On the right side of the report you'll find a list of the zip codes sorted by how many entries from that zip code there are. That list does not correlate with numbers within the dots, but rather the number within the popup that appears when clicking on one of the dots that does not contain a number.