diff --git a/net/cm/README.md b/net/cm/README.md
index 23cf836..7291f3b 100644
--- a/net/cm/README.md
+++ b/net/cm/README.md
@@ -22,7 +22,7 @@ screen
 
 This will fetch `http://download.cyanogenmod.org/` and download `*.zip` `*.img` and check their `sha1`. Then upload it to baiduyun.
 
-The default download directory is `/var/cyanogenmod`, and the default upload directory is `/YOUR_APP_DIR/cm/DEVICE`. Log file is saved in `/var/cyanogenmod/DEVICE/log/DEVICE.log`.
+The default download directory is `/var/cyanogenmod`, and the default upload directory is `/YOUR_APP_DIR/cm/DEVICE`. Log file is saved in `/var/cyanogenmod/DEVICE/log/DEVICE.log`. Files have been uploaded is recorded in `/root/cm/cm.json`, file exists in `cm.json` will not download again. The script check only the last 50 builds, after all uploads are done, it will sleep for 60s and then check again.
 
 **Generate device list**