The Chess.com Tactics Trainer uses the same Glicko rating style used in our Daily Chess and Chess Lessons. Essentially you are playing a quick game against the problem! If you make all the correct moves you can achieve up to a full point for a win, and if you fail then you get a partial score based on how many correct moves you made. This "move score" is then adjusted based on how long you took to solve (or fail) the problem compared to the average solving time. Those scores are put into the Glicko formulas and then both your rating and the problem's rating are adjusted.
The chart below shows how your "move score" is adjusted based on your solving time.
keywords: tactics rating score time solve problem result points