minor: updates to chunkSize in mongos man page

Author: Sam Kleinman

source/reference/mongos.txt

@@ -208,9 +208,9 @@ Options
 .. option:: --chunkSize <value>
 
    The value of the :option:`--chunkSize` determines the size of each
-   :term:`chunk` of data distributed around thee :term:`sharded
-   cluster`. The default value is 64 megabytes, which is
-   the ideal size for chunks in most deployments: larger chunk size
+   :term:`chunk`, *in megabytes*, of data distributed around the
+   :term:`sharded cluster`. The default value is 64 megabytes, which
+   is the ideal size for chunks in most deployments: larger chunk size
    can lead to uneven data distribution, smaller chunk size often
    leads to inefficient movement of chunks between nodes. However, in
    some circumstances it may be necessary to set a different chunk