There are two secretaries in the SSM Act.
Capital S secretary and lower case s secretary.
Capital S secretary is the Commish of Fair Trading or Secretary of the Dept.
Lower case s is the secretary of the OC.
The Secretary of 218 is the capital S variety and referring to the dictionary in the SSM Act
Secretary means—
(a) the Commissioner for Fair Trading, Department of Customer Service, or
(b) if there is no person employed as Commissioner for Fair Trading—the Secretary of the Department Secretary means—
(a) the Commissioner for Fair Trading, Department of Customer Service, or
(b) if there is no person employed as Commissioner for Fair Trading—the Secretary of the Department.
Section 218 is about making application to Fair Trading
The s 216 process is not mandatory and is about an in-house thing if the OC likes.