Clusters for close markers

Close markers hide one another. So people think there is the only marker at that point, they don’t try to close up the map.

I know there is a solution for such problem. ClusterMarker makes unions of close marker into one cluster marker, and it’s baloon says there are N points at this place.

Don’t you want to include this feature or could you suggest me how to include it correctly?

Thank you.

http://ww.wp.xz.cn/extend/plugins/pronamic-google-maps/