I'm here to explain how it works, Gracedc1992.

Journal entries are used as the last resort for entering transactions. You also use this when you transfer money between income and expense accounts. Or, transfer money from asset, liability, or equity to any income and expense accounts. 

You're unable to change the class by creating entries. You'll have to open the transaction and change the class manually.

Then, when you pull up the Sales by Customer report, it will show the transaction's correct class. You can also customize the report to help you focus on the details that you want.

Feel free to get back to us if you have additional questions. We're just around to help you.