Size or weight, whichever costs more
The shipping workbench bills a box on either its size or its actual weight — whichever gives the higher number. A light, bulky box is billed on its size, not its weight. As you type in a box's measurements, the form tells you which of the two yours will be charged on, and by how much.
Why it says Provisional
That price is marked Provisional, because boxes are weighed again once they are actually packed. The number you see while filling in the form is not final until that reweigh happens — the price is confirmed before anything ships.
Confirming what shipped
On delivery, you confirm not just that the parcel arrived but that its contents match what was declared, box by box — a check that protects you and whoever is sending or receiving it.
Where the rest lives
Sending a parcel is placed the same way as any other order — see Ordering and paying for the builder, and Watching the work for how its progress and evidence show up once it is on its way.
Ask Ally
Ask Ally "why does my parcel say Provisional" and it will explain the reweigh step.