From 1 July 2022, employers are required to make super guarantee contributions to their eligible employee's super fund regardless of how much the employee is paid. Employees under 18 must work more than 30 hours in a week. Other eligibility criteria is detailed here.
When calculating the minimum super threshold amount for the month, it is based off the entire gross earnings of the employee, regardless of if the earnings are considered to be ordinary time earnings, however, the super value is calculated off the ordinary time earnings amount.
For example, say you have an employee that is ordinarily paid $25 / hour and $50 / hour for overtime.
In a given month, the employee who is over 18 and works 30 hours ordinary hours and 5 hours overtime, giving the employee a total earnings of $1000 for the month.
This means they are eligible for super but they will only earn super on the 30 hours of ordinary earnings, not the full $1000.
You can find more information about calculating super on the ATO website:
https://www.ato.gov.au/Business/Super-for-employers/
and the Fair Work website