Hi – I can't replicate this myself but this is happening consistently with one user. I've attached details of their OS / Browser if that's important.
Whenever they add an entry it is creating 2.
The form is at http://cmn.unitingcare.org.au/light-a-candle/
You can view entries here: http://cmn.unitingcare.org.au/candles (Only one set of duplicates is visilble. I have deleted previous duplicates).
Please note that there is a separate issue I've logged for this form in case they are related: http://wp-types.com/forums/topic/cred-form-notification-failed/
Cheers, Rob