[ML] Add explanation of typical location (#2753)

(cherry picked from commit ffe6cd0)

docs/en/stack/ml/anomaly-detection/geographic-anomalies.asciidoc

@@ -211,6 +211,11 @@ behavior:
 image::images/ecommerce-anomaly-explorer-geopoint.jpg[A screenshot of an anomalous event in the eCommerce data in Anomaly Explorer]
 // NOTE: This is an autogenerated screenshot. Do not edit it directly.
 
+A "typical" value indicates a centroid of a cluster of previously observed 
+locations that is closest to the "actual" location at that time. For example, 
+there may be one centroid near the user's home and another near the user's 
+work place since there are many records associated with these distinct locations. 
+
 Likewise, there are time periods in the web logs sample data where there are
 both unusually high sums of data transferred and unusual geographical
 coordinates: