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.
A draw, but Mainz 05 created more (1.55 xG against 0.69) — points dropped.
Mainz 05: −1.0 for the season (6 in the table). Paderborn: +1.1 (12). The gap between points and xPTS is built from matches like this one.