Thanks for getting back and adding a screenshot, @ChristineYA.
Allow me to join in this conversation and help you reconcile your account in QuickBooks Online (QBO).
Once you create a credit card account, the program will allow us to enter a negative amount as a beginning balance. This will also reflect as your QuickBooks balance in the Chart of Accounts. However, when viewing the register, its opening balance will show as positive in the PAYMENT column.
If the account was created with a positive beginning balance, this will still reflect as a positive amount but on the CHARGE column.
Please take note that QuickBooks won't allow editing opening balances with a negative amount. That's why you're getting the error message.
In your case, I'd recommend creating a credit card account with a negative beginning balance. Then, move all of your affected transactions to this new account. That way, they would match your actual bank statements.
After editing your transactions, we can deactivate your old credit card account so they won't show up on your list.
Before taking these steps, I'd recommend reaching out to your accountant. They can provide you with the right advice in handling your accounts and making sure your books are accurate.
When everything is fixed, you can now reconcile your accounts in QuickBooks.
Please let me know if you need further assistance in reconciling your accounts. I'm always here to help you out. Have a nice day.