Sales Process - DP return

Hi all,

Hope you can help me for this case.

In company X, they have a common sales process like this:

step 1 - Company X send Sales Order to Customer T with total amount $50000 for 5000m3 boards

step 2 - Customer T pay 1st Down Payment $20000

step 3 - Customer T pay 2nd Down Payment $25000 (which mean, DP total is now $45000)

step 4 - When Company X want to deliver their woods, they calculate again and found only get 4000m3. So they will deliver 4000m3 with total price $40000, which mean, they need to return DP $5000 to Customer T. And then finalized their invoice and send delivery note.

Any better suggestion, how to translate this transaction to SAP Business One ?

Thanks before.

Regards,

Elsa