Deposit with DATA fieldBefore you send coins from your wallet to the exchange wallet, you have to set these 3 fields in your wallet:
(1) First field is where you must copy and paste the exchange wallet address (the wallet address in your user account on the exchange and that's the address you must send the coins to)
(2) Secondly, you have to set/type the deposit amount
(3) Thirdly you must add the DATA field number located in your account on the exchange under the exchange address for deposit. It is the unique number (trader id).
Now, the place to put data field in your wallet is hidden by default in some wallets eg. MyEtherWallet, you have to click on "+Advanced: Add Data",
after clicking you will see the Data field, you have to copy and paste the data field number in your exchange account and paste it in this field in your wallet exactly like in the image below before sending your coins.
This should be like in the image below:
If make a deposit without DATA field to your transaction from your wallet, your deposit will be lost forever because it'll be untraceable.