Usually, it's a visits from internal IP address (like 192.*.*.* or 10.*.*.*) - your company network, monitoring systems, etc.
Such addresses cannot be resolved by MaxMind, so they're just displayed as "Not Found". Also, sometimes you might want to update GeoIP information manually (for example, if you know more about the particular IP than MaxMind does)
The simplest way to do it is to update the DMS database directly. This can be done in 2 easy steps.
