Congratulations, you did it!
I think the first flush is more about actually doing and experiencing it, and not so much about how many big stones came out...
It seems that for many the first flush pushes out a lot of sludge and gunk, that's what mine did. And it seems you had that, plus some stones, so you know you were successful! I had only a couple of stones then, but lots of foul smelling sludge. My later flushes produced more stones, less sludge.
So, keep up the good work! You are on track!