Use square brackets for the proceeding number

Error²Federal courts, Illinois courts21st and 22nd editions

An Australian case name's proceeding number sits in square brackets; round brackets in the same citation already carry the year, the court and the country.¹

1. 1T2.2 Australia. Tables: R. 20.1 Jurisdiction; T10.3 Countries and Regions.
2. 2An error: the rule in note 1 allows one form, and this is not it.