unable to create proforma invoice.

dear all,

here I m facing one issue, this is make to order process.

sales order created with two line items. and with reference sales order Delivery created with delivery qty is line item 10 - 20qity and line item 20 - 23qity.

here we are trying to create proforma, with reference delivery number. but it is taking line item 10 only. it is not taking line item 20. it is showing massage like "Proforma invoice item count and delivery item count are different".

but my order qty is 97 for both line items, delivery qty is line item 10 is 20qty and item 20 is 23 qty we are trying to create same.

please help on this.