How does Create Mass Additions transfer discount from AP to FA

Summary:

I am creating an invoice with 1 asset line. The invoice is validated and accounted and the line is well transferred to Mass Addition. On my invoice I have a payment terms with discount.

I perform a full payment of the invoice. The discount is well calculated. I run the create accounting on the payment and the payment is well accounted.

If I run the Create Mass Additions, I am getting one invoice line with Discount in the report BUT the amount is 0 instead of the discount amount related to my line.

How could this be solved ? Can you give me the rule to generate the correct line.