You're failing to include your BMR cals in your numbers. You'll probably burn about 2000 cals/day even if you never get out of bed.
That is far, far too many calories to be registered as active calories for 16000 steps.
The number of Calories burned during a walk has no relation to the number of steps (as long as your device has a working heart rate monitor). It is only based on your Heart Rate, average Resting Heart Rate, the Heart Rate Variability (for detecting the anaerobic threshold), and on the Resting Metabolic Rate (calculated with your weight, hegiht, gender, age, and Activity Class). So if the Calories burned during walk seam to be too high to you, check out all of those values. You can make some basic estimation using those values - have a look at this thread for the way it can be done.