For silver jewelry, the designs are made either through machine-based manufacturing or hand manufacturing. Normally, while making a design, certain parts of the metal will be wasted while connecting them. Most jewelry items, especially necklaces, are made separately and connected at the end. During the connection process, they will waste some of the metal. They charged these items as wastage.
Source: https://www.quora.com/What-is-making-charge-on-silver-jewelry/answer/Harsh-Garg-59