Barcelona, as is usually the case, is dominating possession 63%-37%. However, Bayern has 8 corner kick's to Barcelona's 2, and Barcelona has only 1 shot (0 on goal).
Possession is meaningless if you can't do anything with the ball. Nothing is taking place because Bayern is controlling the middle of the pitch. Barcelona is allowed to play up, but are quickly met with opposition as soon as they cross midfield with the ball. Therefore, all of the possession has been above 18 yards.