"Furious Pete" was expecting to win at least 40 prizes, under the assumption that the odds were based on the number of stamps. As shown in the video, it didn't end quite as well as he hoped.
After Pete and his wife went through all the monopoly pieces, they discovered they had a grand total of 23 prizes. Most of them were food prizes, meaning they won "a lot of cheeseburgers," as he put it.
In the video, Pete says this makes the odds about 1 in 9, which would be correct if each game stamp had a 1 in 5 chance of winning. However, the Official Rules of the game state that the chances of winning are actually based on the number of game pieces (1 piece = 2 stamps). So in that case, McDonald's was pretty accurate in their odds.
McDonald's Monopoly in Canada. McDonald's Canada
After studying the rules a little too intensely, it appears that only the food prize has a 1 in 5 chance of being won, though; as the prize values go up, the odds go down. The chance of winning $10,000 in cash, for example, is 1 in 13 million.
In all fairness, if we spent $340.68 on McDonald's, we'd expect to win something a little better than a free sandwich too. Unfortunately, that's not how odds work.
h/t Foodbeast