Pro maps will create one wagmp_maps.js file. this will have a line in it for each map that is created.
For each map that is created, it will create a wagmp_map_<int>.js file. <int> is a variable that will start at 1 and increment for each map you create.
On the page, to display the map, there will be a div created as the map place holder:
<div id="wagmp_map_<int>" style="width: 300px; height: 300px;"></div>
the id of the div "id="wagmp_map_<int>"" along with the JS include line:
<script type="text/javascript" src="google_javascript/wagmp_map_<int>.js">/*wagmp*/</script>
control which map is loaded.
The code in the wagmp_maps.js:
if(window.wagmp_map_<int>) wagmp_map_<int>();
is testing for the div ID on the page, and loading the corresponding map.