Why did my HECS not get cleared from my tax return?

To give context I had a $7k HECS debt last FY which deducted the entirety from my tax last year. I switch off my compulsory payments during the year as my income is >$270k so just get the HECS to wash its own face at the end of the year.

This year. $3.8k HECS debt remaining, $302k taxable income. My return has balanced and my HECS updated to $1.7k? I thought it would have paid the whole thing out this year? Given last year it took the whole $7k debt and only my accumulated units stacked up to the $3.8k as I’m still studying.

I am thinking it’s probably best to just pay the remainder out next pay or from my return, but the math isn’t mathing in my head can anyone explain?