It would reset. Selling of shares is a CGT event, so you will have to calculate the gain or loss on that transaction with your original purchase as cost base.
Your purchase today, Friday, is unrelated even if the same stock and quantity and becomes the cost base for calculating the gain/loss whenever todays purchase is sold.
Be careful if selling to generate a tax loss and then immediately buying back the same stock. That is regarded as a wash sale and is frowned upon by the ATO.
