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Hope you’re having a great day @pappyfidel, welcome! I'll be more than glad to give you a tour of the options that you have with the Fitbit Surge to track indoor activities. Fitbit trackers use a 3-axis accelerometer to understand your motions since they have been designed to track step based activities. By analyzing acceleration data, our trackers provide detailed information about frequency, duration, intensity, and patterns of movement to determine your steps taken, distance traveled, calories burned, and sleep quality as a plus. 
When you're tracking indoor activities such as Spinning, Elliptical or Kinetic Rock and Roll, your Surge takes the movements of your body plus your HR (heart rate) information. So, it'll depend of the intensity of the workout that you will get more calories.
Note that while you are doing exercise on your stationary bike or in Kinetic Rock and Roll there is no motion of going forward that your Surge can detect. Your tracker in the most basic form is a movement sensor and if the movement is reduce calories will be affected. That's why we advice to use the option "Workout" in your Surge while using indoor machines and later on edit the name for the activity. When you edit the "Workout" activity, it'll require some details like: distance and speed, other details like calories and time might be changed too in case you need to. This information is edited from your Fitbit App or computer.
Surge has the SmartTrack and Multi-Sport to track your indoor activities to have more accurate information from calories.
Hope this helps to decide if Surge is a good option for you! I'll be around. 
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