Create Single invoice from two deliveries

Hi All.

• I created sales order with two(same) materials, shipping point only differs.
• So i created 2 deliveries for this sales order,according to the shipping point.
• To combine deliveries, In VF04, I select my deliveries and click collective doc/online, in split analysis.it shows like below

• Then i saved and it generates billing document with single item only..
• Even,I changed field assignment number in VTFL to billing or keep it blank.. It creates invoice with single item only..

What else i need to to ???

Thanks,

Yogesh.