Nothing is purely strength without cardio, and nothing is purely cardio without strength.
To maximise the cardiovascular benefits of strength-type movements, you would do much as you are with limiting the weights, repeating quickly, and not worrying too much about form or range of motion (beyond "safe" - always "safe" as a minimum!).
But also, you would ensure you're working your entire body at once, eg combine squats with an arm movement, never do "just a bicep curl" etc. And also do not rest. With ST we can rest between sets, and this is beneficial. With a lighter weight you shouldn't need to and you can continue the cardio effect by ensuring you work consistently, which the DVD almost certainly does for you.
Technically, cardio is defined as:
1. Uses (all or mostly) whole body movements as compared to single muscle movement
2. Raises your HR to 65-85% of your max, and sustains that
3. Lasts 10 minutes or more
If you feel the DVD is matching that, it's good to count it as cardio. As for tracking it, just use a generic "low impact aerobics" (or high impact, if both feet are constantly leaving the ground together).
Deb, in New Zealand