A good target for each body part for hypertrophy.
~13 sets for each Muscle Group per week is apparently a good recommendation by many people in the “science-based fitness” community. Beginners are slightly less than 13, intermediate are maybe slightly over 13.
But also there is a Law of Diminishing Returns with reps. Pareto Principle applies here. You can do a lot with just a little bit of working out. You can maintain with a surprisingly small volume - just one or two good, hard-fought sets per week.
This is ideally split out over two (to 4) workout sessions. So, 7 sets for shoulders on Tuesday, another 6 on Friday.
Note: this is for ideal growth. It’s not necessary for muscle growth. I’ve seen recommendations that suggest this probably recommending a bit too much. It depends on how much you want to train.