What is the difference between "Single object" and "Multi-piece set"? Why is it important?

When you upload your file, we might detect that it contains several parts. We’ll ask you if it’s a single inseparable object or a multi-piece set. A single object is an object that cannot be separated into several pieces (like a chain). If your design can be separated into several pieces (a set of chess pieces for example), you need to let us know by ticking “multi-piece set”, so that we print it as several objects. This allows us to assign each physical object an internal tracking ID for quality assurance. Failing to give us the right information at this stage can lead to lost pieces, delays and degraded production quality.