Subsidiary hazards see 2;0.6.6:

2;0.6.6 Subsidiary hazards must be representative of the primary hazard posed by the other dangerous goods contained within the article. When only one item of dangerous goods is present in the article, the subsidiary hazard(s), if any, is the subsidiary hazard(s) identified in column 4 of Table 3-1. If the article contains more than one item of dangerous goods and these could react dangerously with one another during transport, each of the dangerous goods must be enclosed separately (see 4;1.1.8).

Dangerous goods which are classified with special provision A2, the state variations AU 1, CA 7, IR 3, NL 1 and US 3 are normally assigned. However, these are not recoreded under this UN number.