Calc error? using Credit Note with Invoice

A credit note I created to reimburse a customer is not behaving right.
The credit of $5 shows up as a $4.09 deduction from the customer’s current invoice.
If I INCREASE the amount on the credit note to 5.91 then the deduction on the customer’s invoice shows as the required amount of $5. See below…

I’m a new user so I can only upload 3 images per post. I’ll put the other 2 corrected pics in the following post

After the amount alteration…

Thanks for any help

Your screen shots are not helpful is determining what your issue is.

First, post a screen shot of the Edit screen, not the View, of the credit note in question.

Second, it appears you are using a custom theme for your sales invoice. If so, post a screen shot of the sales invoice in question using the built-in, Plain theme. You are responsible for troubleshooting custom themes.

I figured it out. The customer has OVERPAID the invoice by 91 cents.

After digging a bit…
The [PAID IN FULL] shot of the invoice shows the incorrect $4.91 deduction attributed to the credit note. Presumably that’s how Manager justifies the paid in full as being balanced, (but there was no red overpayment notice).
However, the 0.91 excess shows up as a negative amount in Accounts Receivable on the balance sheet report.
So it’s all good. I just have to issue my customer another credit note for the 91 cents and post it to his next invoice. And Tut, I’m happy with my customised theme AND with Manager too. Good ac prog methinks.