Well ahrz seems to have cleared that issue up

Just to add, the 4 digit number you are referring to is the security batch number for the card. Some websites now ask for you to enter this number in addition to the usaul card and valid dates. You also need to give this number idf you need to change any details on your AmEx account such as your address. You will also use the number when registerign your card for online maintenance of the account.

Thanks,
Richard