DOCS-9849: addShard maxSize

Author: kay-kim

source/reference/command/addShard.txt

@@ -44,8 +44,9 @@ Definition
    Specify a ``maxSize`` when you have machines with different disk
    capacities, or if you want to limit the amount of data on some
    shards. The ``maxSize`` constraint prevents the :term:`balancer`
-   from migrating chunks to the shard when the value of
-   :serverstatus:`mem.mapped` exceeds the value of ``maxSize``.
+   from migrating chunks to the shard when the ``totalSize`` returned
+   from running :dbcommand:`listDatabases` on the shard exceeds the
+   value of ``maxSize``.
 
 
 Considerations