If you want to see the received advance in proforma, Follow below steps.
[A] After you generate OC, Create Receipt for Advance received. As shown below.
[B] Once you have created a receipt voucher for advance payment, Now generate Proforma using the "Create Document" button.
[C] You can see the below image, Advance Payment is included in proforma.
Keywords: ARV Receipt, Advance Payment in Proforma.