The Qantas American Express Ultimate Card - how does the $450 travel credit work?

Since NAB is losing their Amex card, I am looking at new cards to replace it. I have a couple of questions with this particular card. Is the $450 flight bonus for each card or for one account? Also, can you use your point to upgrade when you use the $450 bonus?

The $450 is a travel credit and will show when you log in to your Amex Account under the Travel tab. You will only get one credit per account per year and you must book via Amex Travel and use it in one booking.

Once booked, you can open ‘manage my bookings’ on Qantas website and upgrade from there if upgrades are offered.