To lose weight and keep it off: You will need a high amount of physical activity unless you also adjust your diet and reduce the amount of calories you're eating and drinking. Getting to and staying at a healthy weight requires both regular physical activity and a healthy eating plan. The CDC has some great tools and information about nutrition, physical activity and weight loss. For more information, visit Healthy Weight. Reduce Your Risk of Cardiovascular Disease
If 10 revolutions per minute equal 1 mile per hour, then 1 rpm = 0.1mph. At 25rpm you should br producing 2.5mph, and at 35rpm you should get 3.5mph. I would suggest you measure the length or distance you are actually achieving, and see if this stacks up.
Divide 31,680 by the stride length. For example, if the stride measurement on your machine is 36 inches, divide 31,680 by 36 to get 880. This number is how many revolutions that you need for one mile. Determine the amount of time that it takes to do one mile on your elliptical machine. This is the total number of revolutions to do one mile divided by your average RPMs. If you do 50 RPMs and it takes 880 revolutions for one mile, you need to exercise for 17.6 minutes to do one mile.