Very few I’d guess. This also depends on your personal BMI, BMR and VMO.
Best way to know is to wear a personal tracker, even then it’s an average.
If I had to guess, I’d say about 50, which is about 8 calories a minute.
360 crunches in 6 minutes is about 60 crunches per minute, which is one knee to elbow per second. That’s a nice steady pace that would put someone in a mid-range intensity level for cardio – more than a walk but less than a sprint.