This article explains how the site determines how many calories you should be eating.
I think if you go into your settings, and just change something, it should change your calorie goal back or you, but if that doesn't work try this:
Go to the sparkstart page. You'll see on the left side, this bar that has something about how many more calories you can eat today, how many more calories to burn in the week, and then how many lbs you've lost. Under the "___ pounds lost", your goal ("goal to go from ___ to ___ by ___" should be there with a little link that says "change goal." Click on that. Update your goal by putting in your current weight and completing that part again.
It should revert your daily calorie goal back to what it should be using the initial calculations!
I think if you change your weekly calories burned goal, it changes your calorie goal back, too, but I KNOW it works by changing your weight loss goal. Remember to keep the weight loss goal (current lbs) updated to ensure you are getting the right calorie range, because you will probably have to start eating less to see the same weight loss as you lose a lot of weight.