Apply suggestions from code review

Co-authored-by: Alexander Spies <[email protected]>

docs/reference/esql/processing-commands/stats.asciidoc

@@ -16,7 +16,7 @@ The name by which the aggregated value is returned. If omitted, the name is
 equal to the corresponding expression (`expressionX`).
 
 `expressionX`::
-An expression that calculates an aggregated value.
+An expression that computes an aggregated value.
 
 `grouping_columnX`::
 The column containing the values to group by.
@@ -35,10 +35,10 @@ include::../functions/aggregation-functions.asciidoc[tag=agg_list]
 NOTE: `STATS` without any groups is much much faster than adding a group.
 
 NOTE: Grouping on a single field is currently much more optimized than grouping
-      on many fields. In some tests we've seen grouping on a single `keyword`
-      field to be five times faster than grouping on two `keyword` fields. Don't
+      on many fields. In some tests we have seen grouping on a single `keyword`
+      field to be five times faster than grouping on two `keyword` fields. Do not
       try to work around this combining the two fields together with something
-      like <<esql-concat>> and then grouping - that's not going to be faster.
+      like <<esql-concat>> and then grouping - that is not going to be faster.
 
 *Examples*