[Maps][docs] add more details to Quantitative data driven styling docs

docs/maps/maps-aggregations.asciidoc

@@ -2,10 +2,25 @@
 [[maps-aggregations]]
 == Plot big data without plotting too much data
 
-Use {ref}/search-aggregations.html[aggregations] to plot large data sets without overwhemling your network or your browser.
+Use {ref}/search-aggregations.html[aggregations] to plot large data sets without overwhelming your network or your browser.
+When using aggregations, the documents stay in Elasticsearch and only the calculated values for each group are returned to your computer.
 
 Aggregations group your documents into buckets and calculate metrics for each bucket.
-Your documents stay in Elasticsearch and only the metrics for each group are returned to your computer.
+Use metric aggregations for <<maps-vector-style-data-driven, data driven styling>>. For example, use the count aggregation to shade world countries by web log traffic.
+
+You can add the following metric aggregations:
+
+* *Average.* The mean of the values.
+
+* *Count.* The number of documents.
+
+* *Max.* The highest value.
+
+* *Min.* The lowest value.
+
+* *Sum.* The total value.
+
+* *Unique count.* The number of distinct values.
 
 Use aggregated layers with document layers to show aggregated views when the map shows larger
 amounts of the globe and individual documents when the map shows smaller regions.

docs/maps/vector-style.asciidoc

@@ -45,11 +45,17 @@ image::maps/images/vector_style_dynamic.png[]
 
 Quantitative data driven styling symbolizes features from a range of numeric property values.
 
-To ensure symbols are consistent as you pan, zoom, and filter the map, quantitative data driven styling uses {ref}/search-aggregations-metrics-extendedstats-aggregation.html[extended_stats aggregation] to retrieve statistical metadata.
+Property values are fit from the domain range to the style range on a linear scale.
+For example, let's symbolize <<add-sample-data, Kibana sample web log>> documents by size.
+The sample web logs `bytes` field ranges from 0 to 18,000. This is the domain range.
+The smallest feature has a symbol radius of 1, and the largest feature has a symbol radius of 24. This is the style range.
+The `bytes` property value for each feature will fit on a linear scale from the range of 0 to 18,000 to the style range of 1 to 24.
 
-Click the gear icon image:maps/images/gear_icon.png[] to configure extended_stats. Set *Sigma* to a smaller value to minimize outliers by moving the range minimum and maximum closer to the average. Clear the *Calculate range from indices* checkbox to turn off the extended_stats aggregation request.
+To ensure symbols are consistent as you pan, zoom, and filter the map, quantitative data driven styling uses {ref}/search-aggregations-metrics-extendedstats-aggregation.html[extended_stats aggregation] to retrieve statistical metadata. Extended_stats is not available for numeric property values from the <<maps-aggregations, metric aggregations>> count, sum, and unique count.
 
-NOTE: When the *Calculate range from indices* checkbox is cleared, symbols might be inconsistent as users pan, zoom, and filter the map. Without extended_stats, the range is calulated with data from the local layer. The range is recalulcated when layer data changes.
+To configure extended_stats,click the gear icon image:maps/images/gear_icon.png[] to configure extended_stats. Set *Sigma* to a smaller value to minimize outliers by moving the range minimum and maximum closer to the average. Clear the *Calculate range from indices* checkbox to turn off the extended_stats aggregation request. The gear icon is not available for numeric property values from the <<maps-aggregations, metric aggregations>> count, sum, and unique count.
+
+NOTE: When extended_stats is not used, symbols might be inconsistent as users pan, zoom, and filter the map. Without extended_stats, the range is calculated with data from the local layer. The range is re-calculated when layer data changes.
 
 [role="screenshot"]
 image::maps/images/extended_stats_config.png[]