Residual material may carry over into later batches of the same product if adequately controlled (for example residue on micronizer walls, damp crystals in a centrifuge bowl, or incomplete discharge of a vessel), but it should not carry degradants or microbial contamination that would change the established impurity profile. Production should be run so that other materials do not contaminate intermediates or APIs, and extra care should be taken in handling APIs once purified.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.