Game Mechanics Questions - Drop Priority

[WorldGovernment]

I'm pretty sure the custom drops doesn't fill any of the base slots.
As for why it's 8, almost all monsters officially drop 8 items. Not sure if it's the maximum though.

If Wings are calculated first (have priority) and Honey / Item drop.
Slot 6: Honey
Slot 7: Item

There is only one slot left for Headgear drops. Meaning BB will drop xor DB will drop. Esentially reducing (By a negligible amount) the drop rate of BBs
Slot 8:

then it would make the things he mentioned to be placed at slots 9,10 and 11 then?