Creditors balance on the trial balance does not equal to the total of all outstanding suppliers invoices. where am i going wrong?

Hello, PP17. 

Let's go ahead and try to run the Trial Balance report to get the total amount of the correct transactions. Also, when entering an opening balance an income and accounts receivable (A/R) is impacted for debtors, and expense and accounts payable (A/P) account for creditors. The reports are selected as the default account when you created your account. 

For more insights about the balance, you visit the article I recommend below:  

How to set up customer or supplier opening balance. 

If you have any follow up questions, please let me know. I'm here for you. Have a great day.