Truth be told, you have to establish a personal comfort level. Look at all of the internet talk about any gun. You will see people advocate for 100, 200, 300....., 1000, etc., rounds for "break in". You will see all ranges of round count failures from single digits to approaching 1000+ rounds. There is no right answer. The fact of the matter is that for every single, subsequent, violent action of the slide which happens upon firing, wear occurs. Each subsequent shot is more likely to cause a mechanical failure than the previous. Each subsequent shot causes more wear, even if ever-so-slight, than the immediately prior shot. That's a fact. There is no "correct" answer. With the benefit of hindsight, you will know at the round count of your failure, you should have stopped breaking it in multiple rounds before that. Hopefully, your "break in" does not stop just one round prior to failure. We can never be that precise. We just have to establish our own comfort level and personal feel.