Why has turbotax put in an amount for line 323 (tuition and education amounts) when I have nothing to claim? I'm getting an Audit error now... How do I edit/remove this?

If you used the CRA Auto-Fill, they may have imported some incorrect information: https://turbotax.community.intuit.ca/replies/3475149

Yes obviously... But how do I edit the information?

From the "How can I verify if I was impacted by this issue?" part of the answer.

In the Find window, type Tuition fees carryforward and select Go.

On the Tuition fees carryforward step:
If you have unused tuition amounts for carryforward on your CRA Notice of Assessment for tax year 2016, confirm that the amounts in TurboTax match the amounts on your NOA and select Continue.
If you do not have unused tuition amounts for carryforward on your CRA Notice of Assessment for tax year 2016, remove the amounts from both the federal and provincial fields and select Continue.