Welcome, rabowman. I'm also new here and have over 150lbs to lose for all the same reasons.
To your question, LisaAnnie's advice is right on. It's something I had to figure out as well. For instance, I show that the system calculates that I burn 166.5 calories/hour in my sedentary job, versus 92/hour when I sleep. Adding the activities should help you get a better idea.
I'm not paying strict attention to the calorie balance, thinking what the system suggests is my maintenance level may be a little inflated. Instead I'm trying to focus on my goal calories (2,000 for me). For what it's worth, after my first complete week or religiously logging activity and calorie consumption my weight loss almost exactly matched what could be expected from the calorie balance fitday showed. It will be interesting to see how well it matches beyond the first week.
If I can give you one small piece of advice that I feel has helped me in a lot of ways it is to really try to drink as much water as you need. I've been drinking a minimum of 150oz/day based on advice i got here and I think it has contributed not only to how good I feel, but I'm missing the signs of dehydration in my appearance. I'm sure that if I wasn't consuming as much water I would have appeared to have lost more weight, but now I can feel confident that the weight I have lost is "real" weight loss and not just water that will fluctuate with my hydration.
Best of luck to you!