It's unique to see that Real Madrid's chances are only 31% to win, because they are the defending champions, and their chances should be greater even play away at the Emirates.
I am sure Ancelotti knows what he was doing. It's not the first time Real Madrid met Arsenal; they even met on the ICC (2019), the Emirates Cup (2008), and the UCL (2006), but Real Madrid did not win it all! Guy, in the last 4 matches, Arsenal won 2 matches, and the rest were a tie. This could be homework that should be fixed immediately because in La Liga, Real Madrid also has a problem with the squad; they lost when met Valencia, and it seems their focus was split between the Copa del Rey final, which drained their energy.
With so many Real Madrid players in the hospital, it's surprising that Arsenal's chances are estimated at less than 50%
But in fact, in previous seasons, Real was mostly an underdog against almost all the big teams, and in this pair, Real is the favorite, but Arsenal's chances are estimated to be higher in this first game. Perhaps Real's status will change after the first game, but for now they are the favorites if we are talking about a two-match confrontation.