Tax Return HELP repayment too high?

I started my tax return last week after my employer confirmed my income, but I stopped because the calculator is saying that I'm supposed to pay back over $4600 in the 'Compulsory Higher Education Loan Repayment' on a taxable income of just over $65k.

The ATO documentation for HELP repayments says it should be 3% of the taxable income though: $1950. This is confirmed by the ATO's online calculator for education repayments also. The discrepancy is turning a small tax refund into a significant tax repayment.

I was hoping it was a bug or somesuch, but over a week later the estimate hasn't changed. The ATO's live chat seems to have no clue. Does anybody here have any idea what's going on? Thanks.

\[EDIT\] I use salary packaging to maximise super contributions pre-tax and that massively increased my HELP repayment threshold.