number indicating the relative serviceability (3.37.1) [capability of a facility (ISO 15686‑10:2010, 3.8)] for a user (ISO 15686‑10:2010, 3.34), group, or customer for one topic (ISO 15686‑10:2010, 3.33) on a predetermined supply scale (ISO 15686‑10:2010, 3.27) from the level of the least (serviceability) to the level of the most (serviceability)