[qwerty456127]

I see. Thank you for explaining. The case you describe didn't come into my mind. Nevertheless I doubt counting is important. Some reps less, some reps more, I believe the feeling you always feel when you've done enough. Or you can set a timer - it's not the number that matters, it's the time you spend under the load anyway.

On the other - the way you do an exercise, small details in your posture and the sequence of changes in it - that's what decides if what you do is going to make you more fit/strong, have no effect or just cause pure harm. It's extremely important (at least, in the beginning) to have somebody qualified to watch how you do it and correct you. Many people prefer to train alone though so they need such an app.