Hey
You can do either Pure Cardio and Cardio Abs back-to-back, or you can split them up. It is meant to be done the same day though. Cardio Abs is just an Ab workout video with some cardio mixed in. It's about 20min in length. If you don't think you can do them back-to-back, go ahead and split them up

I have split them up AND I've done them back-to-back. I mostly like to do them back-to-back because I don't want to make time to workout twice. Although, when I did them separately I was able to do more of Cardio Abs, because I wasn't as tired. Do whatever you are more comfortable with, and see how it works out for you.
Andrew