...
Rules and recommendations in this standard are classified into three levels (see Priority and Levels Risk Assessment). Emphasis should be placed on conformance Level 1 (L1) rules. Software systems that have been validated as complying with all Level 1 rules are considered to be L1 Conforming. Software systems can be assessed as L1, L2, or fully conforming depending on the set of rules to which the system has been validated.
...