add notes of corss-reference

Author: MongoCaleb

source/sdk/flutter/sync/manage-sync-session.txt

@@ -119,8 +119,9 @@ ranges from ``0.0`` to ``1.0``. At ``1.0``, the progress stream is complete.
 
 .. tip::
 
-   Use the ``progressEstimate`` to display a progress indicator or estimated
-   data transfer percentage.
+   You can also configure sync monitoring by using the 
+   :ref:`onProgressCallback <flutter-progress-callback>` when you first open a 
+   Realm.
 
 .. _flutter-monitor-network-connection:
 

source/sdk/flutter/sync/open-synced-realm.txt

@@ -64,12 +64,19 @@ to open a realm immediately and sync data in the background when an internet con
 .. literalinclude:: /examples/generated/flutter/open_flexible_sync_realm_test.snippet.async-open.dart
    :language: dart
 
+.. _flutter-progress-callback:
+
 To track the state of the synchronization, pass a :flutter-sdk:`ProgressCallback <realm/ProgressCallback.html>`
 to the optional named argument ``onProgressCallback``.
 
 .. literalinclude:: /examples/generated/flutter/open_flexible_sync_realm_test.snippet.async-open-track-progress.dart
    :language: dart
 
+.. tip::
+
+   If you want to configure progress notifications *after* opening a realm, use 
+   :ref:`SyncSession.getProgressStream <flutter-monitor-sync-progress>`.
+
 To be able to cancel a synchronization in progress, pass a `CancellationToken
 <https://pub.dev/documentation/cancellation_token/latest/cancellation_token/CancellationToken-class.html>`__
 instance to the optional named argument ``cancellationToken``.