diff --git a/weed/command/filer_remote_sync.go b/weed/command/filer_remote_sync.go
index c55544925..bceeb097e 100644
--- a/weed/command/filer_remote_sync.go
+++ b/weed/command/filer_remote_sync.go
@@ -40,7 +40,7 @@ func init() {
 	remoteSyncOptions.filerAddress = cmdFilerRemoteSynchronize.Flag.String("filer", "localhost:8888", "filer of the SeaweedFS cluster")
 	remoteSyncOptions.dir = cmdFilerRemoteSynchronize.Flag.String("dir", "", "a mounted directory on filer")
 	remoteSyncOptions.readChunkFromFiler = cmdFilerRemoteSynchronize.Flag.Bool("filerProxy", false, "read file chunks from filer instead of volume servers")
-	remoteSyncOptions.timeAgo = cmdFilerRemoteSynchronize.Flag.Duration("timeAgo", 0, "start time before now. \"300ms\", \"1.5h\" or \"2h45m\". Valid time units are \"ns\", \"us\" (or \"µs\"), \"ms\", \"s\", \"m\", \"h\"")
+	remoteSyncOptions.timeAgo = cmdFilerRemoteSynchronize.Flag.Duration("timeAgo", 0, "start time before now, skipping previous metadata changes. \"300ms\", \"1.5h\" or \"2h45m\". Valid time units are \"ns\", \"us\" (or \"µs\"), \"ms\", \"s\", \"m\", \"h\"")
 }
 
 var cmdFilerRemoteSynchronize = &Command{
@@ -54,6 +54,11 @@ var cmdFilerRemoteSynchronize = &Command{
 
 		weed filer.remote.sync -dir=/mount/s3_on_cloud
 
+	The metadata sync starting time is determined with the following priority order:
+	1. specified by timeAgo
+	2. last sync timestamp for this directory
+	3. directory creation time
+
 `,
 }