diff --git a/README.md b/README.md
index 05b2aca..0c3ca44 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 
-NOTE: this package only support FPS ID (MerchantID), it doesnt support mobile number / email as recipient identifier. 
+NOTE: this package only support FPS ID (MerchantID), it doesnt support mobile number / email as recipient identifier. The mobile number is just a field in Additional Data in CommonQR Code Specification.
 
 ## node-hk-fps
 A Nodejs module that help to generate QR code content string of the Hong Kong Faster Payment System. Please refer the [blog](https://medium.com/@ryanchanplc/understanding-the-qr-code-used-in-hong-kong-faster-payment-system-6cc1671405d2)