For each weaker clarity, the visual difference between the two clarity grades increases. With experience, experts can judge whether a stone, for instance, qualifies as a better SI1 or a weaker SI1. To indicate these distinctions, Venus Jewel classifies clarity grades into 'better' (+), 'standard' ( ), and 'weaker' (-) categories within each grade.

Additionally, since SI2 has a broad range, it is further subdivided into SI2 and SI3, each with its own subgrades of 'better' (+), 'standard' ( ), and 'weaker' (-).