Steps I have made: 

• Create Analytic account

• Create Project and set this Analytic Account

• I have multiple Sales Orders assigned to this Analytic Account

• Create Purchase Order with product type 'Can be expensed' and set Analytic Distribution

• Confirm Receipt and Vendor Bill

After these steps, all my 'Re-Invoice' products appears in ONE Sales Order. 

QUESTIONS: 

1. How system selects, on which SO should re-invoice products appear? 

2. Is it possible to specify somewhere, on which SO this re-invoice product should appear?