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.
Lazio won against the run of chances: Bologna created more (2.06 xG against 0.81).
Bologna: −6.0 for the season (18 in the table). Lazio: +5.0 (3). The gap between points and xPTS is built from matches like this one.