How do I add a seller discount to an invoice?

[jamimishke]

Hope someone is awake at this hour to help. I am trying to send an invoice but cannot put in a seller discount. I have tried the following but each time it says" the amount must be lower than $0.00

-$10.00, -10.00, -10, -$10.

I think you get the drift, all of these amounts are less than 0.00

am I doing something wrong with the minus button or should it be a different button I need to use?

I have removed the postage cost as the buyer is picking up multiple items, no problem there.

I changed the invoice to local pick up, no problem there either .

However I am trying to give her a $10 discount as she is a regular buyer and it will not let me do it.

Thanks in advance from one night owl to another