The response code is the authorization code, that will be different for every transaction.

If the transaction had an error/decline type status (E/D), then the response_code can be used to help determine why it was declined (but there should only be a generic form of decline message shown to any customer, such as something like ‘Sorry, we are unable to process your transaction at this time). 

The decline codes are for the merchants (internal use), not the customers.