Movement along a curve is called an expansion or contraction, shifts are called increase or decrease. It's also important to realise in this case even if demand increased (shift to the right) it wouldn't necessarily translate into a higher quantity traded. This is because suppliers are less willing to engage in trade (shift in supply curve to the left). Hope this clears things up.
What got me, was thinking that a higher AUD would make suppliers
more willing to sell, since they stand to make greater profit per unit of currency. Consequently, I assumed that supply would increase. I didn't consider the improvement in their investment as being a factor that would decrease supply (or think of it at all) - although I did spend the last 5 minutes staring at this MC trying to determine whether it was an increase or a decrease. I made the wrong choice haha.
I didn't pick up on the 'increase' either, I suppose that was the clue - what I described was an expansion in supply.