If you look at section 2 to begin with, you see that it establishes that the salaries mentioned in this act are payable out of the consolidated revenue fund.
Then when you go through the statute, you will find that salaries are specified and increases are indexed, but the Prime Minister shall be paid a salary of a certain amount, and ministers of state who preside over ministries of state shall be provided a salary of a certain amount. That is the salary.
What you've drafted is a statutory rule that provides that the salaries of ministers of state cannot exceed the salaries of others, but you haven't established the salaries themselves.