Referral code is treated as the provider mark for a transfer. To provide a better insight about users' transfer behavior, you can attach your referral code to cBridge gateway.
Referral code inside cBridge website
You can attach your referral code to cBridge website. When user uses the URL with referral code, cBridge website will help build relationship between your referral code and user's on-chain transaction. Here is the sample link for the referral code
Please use the correct parameter key for referral code, which is ref. Otherwise, cBridge website will not recognize your referral code
Referral code through cBridge SDK
When integrating with cBridge SDK, you can establish relation between your ref code and user's on-chain transaction by posting markRefRelation request to cBridge gateway. You may refer this for more details.