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.
Como created more (2.29 xG against 2.26) and left with nothing.
Frosinone: +4.8 for the season (6 in the table). Como: +0.9 (8). The gap between points and xPTS is built from matches like this one.