One thing I'll mention is that unless your errands get your heart rate up into the cardio zone, I probably wouldn't count those as exercise. If you've been active like this for a long time, it's a normal part of your day to your body, and additional exercise is going to shake things up. This Ask the Expert explains whether or not you need to adjust your calorie range for your active lifestyle: www.sparkpeople.com/community/ask_the_expe
So as long as your calories burned goal reflects the amount of exercise you're doing, you should be fine to eat in the calorie range SP has set for you. If you burned 500 calories more than you consumed per day, that would equal about a 1 pound weight loss each week (since 3500 calories equals one pound.) Keep in mind that our bodies are complicated and don't always cooperate with how the math works out, but if you stay on track with a 400 calorie differential per day, the math works out to around a 3/4 pound loss each week.
Hope that helps!