fix typo in reference/database-statistics.txt

Author: jrassi

source/reference/database-statistics.txt

@@ -40,7 +40,7 @@ Or:
 
 .. note::
 
-   Because scaling rounds values to whole number, scaling may return
+   Because scaling rounds values to whole numbers, scaling may return
    unlikely or unexpected results.
 
 The above commands are equivalent. See the :dbcommand:`dbStats`