There are a couple of reasons why your balance may appear other than you expected:

We are updating charges. During add/drop, the Business Office updates charges daily every morning which refreshes everyone's tuition. If you added or dropped credits, this change will be reflected after we update tuition again. 

You just registered for classes and were not yet billed. 

Please check your student account in about an hour and create a new support ticket if you still cannot see your tuition.