query with s943 info struture updation ..double entry

hi

When i try to create indirect sales order and its billing (lets say 8.5 qty) , its qty gets doubled in s943 table.value coming is 17.so incorrect data flows to BW.thus there is discrepancy of data in SAP vs BW.

Can you please guide that when invoicing is done, how these s943 table is updated in background.logic behind it.

What action shall i take to avoid those duplicate entry in s9437.

Please help urgent

Thanks

Sachin