When SP calculates your calorie range, it assumes an average amount of activity throughout the day. If you've got an active job that requires you to be moving around all day, you might need to increase your calorie range to account for that. Here's an Ask the Expert that will help you figure out if that's the case: www.sparkpeople.com/community/ask_the_expe
If you are just standing but not moving around, you might be burning more than someone who sits all day, but I don't know that it would be enough of a difference to have an impact on your weight loss progress. My guess is that the difference is minimal.
Hope that helps,