The first goal has a very low xG because most shots from that distance do not result in a goal. 2nd goal will have a high xG because it’s a perfect ball close to the goal. The third goal will have a lower xG because headers are lower xG in general and Ronaldo was under significant defensive pressure.
The first goal will have done most of the heavy lifting here.
edit: sorry xG measures how likely it is for a goal to be scored from a certain position. More sophisticated models take into account multiple different factors like defensive pressure, the position of the keeper and the height of the ball when struck, among other things, to further value the chance of a goal being scored in a given situation.