The score says how it ended. xG says how it should have ended: it is the sum of the chances each shot was worth, not an opinion about the game.
Levante created more (2.67 xG against 2.47) and left with nothing.
Levante: −1.4 for the season (17 in the table). Barcelona: +2.6 (1). The gap between points and xPTS is built from matches like this one.