I have an assembly of a few sheet metal parts. In the BOM there appear two items for the same part and the balloon does not attached properly. In the attached image, the balloon attaches for example to part 8.1 when I actually want it to attach to part 8. Consequently, the part quantity is not shown correctly next to the balloon. The parts that have this problem are parts that I can flatten.

How can I attach the balloon to the desired part and show the correct quantity?