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.
Venezia created more (3.19 xG against 2.45) and left with nothing.
Venezia: −5.5 for the season (20 in the table). Lecce: +3.8 (12). The gap between points and xPTS is built from matches like this one.