White lost less because the rating deviation of both people is important.
Black's rating is almost completely unknown so white can't lose many points for losing to someone whose rating is so uncertain.
There's an explanation here:
en.wikipedia.org/wiki/Glicko_rating_systemYou can see from the formula that the starting rating is what's used.
Also quote: After a game, the amount the rating changes depends on the RD: the change is smaller when the player's RD is low (since their rating is already considered accurate), and also when their opponent's RD is high (since the opponent's true rating is not well known, so little information is being gained). The RD itself decreases after playing a game, but it will increase slowly over time of inactivity.
