Yes there three extra calculations that have been added.
"RealPrice" which calculates a discounted price based on the quantity. This is the value in the Price column.
"TotalPrice" which is RealPrice * Quantity. This is the value in the Total column.
"SubTotal" which is TotalPrice / 1.1 (Which removes the GST component). This is the value in the Sub-Total (Excluding 10% GST)
It's a bit of a round about way of doing things but the client wanted the GST componant to be removed and then added back in the confirm form only if the shipping country was Australia.
I also did modify the GrandTotal() method to take it's value from "SubTotal" so that it computed correctly.
Here is me test environment:
You will have to login using the following credentials:
Email Address: email@example.com