Master carton
The master carton is the outer corrugated shipper that actually sits on the pallet. Inner packs and eaches live inside it. Pallet TI-HI, CBM lines and DIM all want the outer dimensions of this carton, including the flute, not the product. FBA box rules are separate from FBA pallet rules.
If the master is 16 × 12 × 10 in and the inner is 8 × 6 × 10 in, the pallet tool gets 16 × 12 × 10. The inner pack only matters for case pack and labeling.