It's nice to see you here, @jw102443!
Let's edit your customer's invoice, then you must be good to go.
- Go to Sales.
- Select Invoices.
- Find and click to open your customer's invoice.
- Enter the correct amount.
- Click Save and close.
Once completed, you can now be able to enter the correct amount of customer's invoice.
Let me know if you have any other questions in the comment section below. It'll be always my pleasure to help.