Logistics couriers don't just charge by actual weight; they charge for the space a package occupies in the delivery truck. The formula (L × W × H) ÷ 5000 converts cubic centimeters into volumetric kilograms.
If actual weight is 450 grams but package dimensions are 25 × 20 × 10 cm, the volumetric weight is 1.0 kg. The carrier will charge you for the higher 1.0 kg slab. If hub scanners misread dimensions by just 1 cm, you jump another slab.