[V2] Update create-datastore.rst (aws#9880)

Author: github-actions[bot]

awscli/examples/medical-imaging/create-datastore.rst

@@ -1,6 +1,6 @@
 **To create a data store**
 
-The following ``create-datastore`` code example creates a data store with the name ``my-datastore``. ::
+The following ``create-datastore`` code example creates a data store with the name ``my-datastore``. When you create a datastore without specifying a ``--lossless-storage-format``, AWS HealthImaging defaults to HTJ2K (High Throughput JPEG 2000). ::
 
     aws medical-imaging create-datastore \
         --datastore-name "my-datastore"