The Map Objects List View is a summary of what your map is currently displaying to you. The left hand list will tell you what the right hand map is currently looking at. 

the map view does auto culling which simply means that when there are too many objects of a certain type the map will only display one icon with a number (ex. 10) instead of 10 icons. There are also filters available by dropping down the filter button to see the possible choices. 

In addition to filtering and auto-culling there is also zoom level visibility, this means that at a high zoom level or far away you will not see information that is found on a street view level (Hydrants, Doors, Knox Box locations, etc.)

And another great thing to know it that as you move aroudn in the map view you will notice a grey crosshair that will be the center of the map indicator, when this gets closer to an object you can see the changes in the left hand list view and the corresponding distances from both the crosshair and from your own location to the listed objects.