What does the shipping estimate on a listing mean?

Listings where the seller has entered box size and weight show a shipping estimate for your location, spread across the pieces: a $24 box across an 80-piece lot adds $0.30 a piece.

At checkout, shipping becomes its own line at the carrier rate, unless the listing says free shipping, in which case the seller covers it and there is no shipping line.

It is an estimate, not a quote. The checkout line is the real number.