Thread: Does rep amount really matter?

Hello,
I have been training for two weeks with resistance bands at home and its been great. But I find myself doing about 20 reps each exercise. Is this okay for building muscle? Ive heard that its best to aim for 10-15 reps for muscle hypertrophy, but it seems to me like its just a number. Muscles arent gonna punish you for increasing that number? I mean, I feel my muscles fatigued at about 20 reps, so I get im tearing muscle tissue. Isnt that what ultimately causes muscle growth?