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.
The score matched the game: Auxerre was the better side by chances too.
Auxerre: +0.3 for the season (10 in the table). Brest: −4.8 (11). The gap between points and xPTS is built from matches like this one.