docs: fix callouts

docs/reference/search/field-stats.asciidoc

@@ -270,18 +270,20 @@ If missing, the format configured in the field's mapping is used.
 [source,js]
 --------------------------------------------------
 curl -XPOST "http://localhost:9200/_field_stats?level=indices" -d '{
-   "fields" : ["answer_count"] <1>
-   "index_constraints" : { <2>
-      "creation_date" : { <3>
-         "min_value" : { <4>
+   "fields" : ["answer_count"]
+   "index_constraints" : {
+      "creation_date" : {
+         "min_value" : {
             "gte" : "2014-01-01",
-            "format" : "date_optional_time"
+            "format" : "date_optional_time" <1>
          },
          "max_value" : {
             "lt" : "2015-01-01",
-            "format" : "date_optional_time"
+            "format" : "date_optional_time" <1>
          }
       }
    }
 }'
---------------------------------------------------
+--------------------------------------------------
+
+<1> Custom date format