You have 30 locations to plot on the map. When the page loads, you see the message in the lower left corner of the map showing the progress of the data load. It loads pretty fast, but stops when it gets to 20. The last 10 locations don’t load.
You are displaying locations in SP2013 v10.9.42.2013 and using the BingTM Map Provider.
Although some locations are displayed, no more than 20 will be displayed if a column hasn’t been configured for each of the geocoding parameters. For example, the screen shot here shows no column selected for Address. When this is the case, only the first 20 locations will be displayed.
To display all the locations, be sure a column is configured for Address, City, State/Province, and Country/Region.
NOTE: The columns configured for each geocoding parameter do NOT need to contain data. The column values may be blank.
This is not a requirement if using the GoogleTM map provider in SP2013.