The description was incorrect

Looked like a copy and paste from another aggregation

docs/reference/search/aggregations/bucket/missing-aggregation.asciidoc

@@ -16,7 +16,7 @@ Example:
 }
 --------------------------------------------------
 
-In the above example, we calculate the average price of all the products that are currently in-stock.
+In the above example, we get the total number of products that do not have a price.
 
 Response:
 
@@ -31,4 +31,4 @@ Response:
         }
     }
 }
---------------------------------------------------
+--------------------------------------------------