When the Bills deferred and the Ravens (obviously) chose to receive the kick, the Bills took the wind with them in the first quarter (rather than give the Ravens the ball and the wind). In the second half, the Ravens chose the reverse, to have the wind with them in the fourth quarter, allowing the Bills first drive to be with the wind. Kind of repeating what others have said, but the Bills only get to choose which direction they want to start in one half (in this case, the first), and they chose to have the Ravens opening drive into the wind.