Here is an example if that can help you. You are under age 50. You salary sacrifice $20,000 and your employer pays a compulsory super contribution of $10,000 (the 9% you refer to).
Concessional Contributions
Salary Sacrifice 20,000
Employer Contributions 10,000
Total 30,000
Limit 25,000
Excess 5,000
If you add such excess, you will have to pay the following tax on the excess part:
Tax Payable On Excess (31.5% + 15%) * 5,000 = 2,325
