Are you talking about which option to use on the FS exercise options? I use my heart rate monitor to tell me how many calories I've burned, and then I select "other" and enter it manually. Many members have discussed that the exercise options frequently overestimate calorie burn by a long shot, so if you're going to use them, I would 'underestimate' the intensity to get a more realistic calorie burn.
Someone who is busier than you is working out right now.
There will come a day when you can no longer do this. Today is not that day.