Update README.md

Author: nateps

README.md

@@ -205,7 +205,7 @@ Populate the fields on `doc` with a snapshot of the document from the server, an
 fire events on subsequent changes.
 
 `doc.ingestSnapshot(snapshot, callback)`
-Ingest snapshot data. This data must include a version, snapshot and type. This is used both to ingest data that was exported with a webpage and data that was received from the server during a fetch.
+Ingest snapshot data. This data must include a version, snapshot and type. This method is generally called interally as a result of fetch or subscribe and not directly. However, it may be called directly to pass data that was transferred to the client external to the client's ShareDB connection, such as snapshot data sent along with server rendering of a webpage.
 
 `doc.destroy()`
 Unsubscribe and stop firing events.