It depends on the level of fitness. A very obese unfit person will burn a lot more calories walking slowly on a treadmill than an athelete running uphill.
I think you are looking at it the wrong way. A novice should use a range of equipment at a rate he or she feels comfortable - the aim is to get used to exercise without causing injury.
When you know what you are capable of, you can set realistic, achievable targets - to increase the intensity of the exercise and the time.
Trust me - any amount of exercise will be beneficial, if you have not been exercising.
Enjoy finding your limits and capabilities. You should be sweaty but still able to talk during exercise.
As you progress, invest in a heart rate monitor.
Don't forget the resistance exercises - use the weights AFTER the cardiac exercise for maximum benefit. Don't go mad - light weights, low reps to start.