Trade Credit allows a business to better match the timing of cash outlays for the cost of goods sold with the cash receipts from sales. (perfectcreditagain.com)
In the example of a Toronto - Calgary flight, Aeroplan miles have decreased in value as they have increased the amount of cash outlay required to redeem the flight. (creditwalk.ca)
So since it's giving you a CoC ROI of 9.89 %, it must be assuming an initial cash outlay of -LRB-($ 281.73 x 12) / 0.0989) = $ 34,183.62. (biggerpockets.com)