How is the rating points given or taken away in dominoes?

when i beat an opponent i generally get about 12 points added to my score when I loose to an opponent I generally loose 20 or more points i thought it might be because of how much you win or loose by but that is not the case. Just curious as to how it is decided.How is the rating points given or taken away in dominoes?
You must be a very good player. Your opponents are lower-rated than you are.



If you win against a lower-rated player, you get less points than

if you were to win against a higher-rated player.

You generally gained only 12 points for winning against a lower-rated player.



If you lose against a lower-rated player, you lose more points than

if you were to lose against a higher-rated player.

You generally lost 20 points for losing against a lower-rated player.