How much damage does a stone sword do to full iron armor in minecraft?

I re watched one of my videos on you tube, I was fighting a guy in full iron armor on minecraft survival games, and I got seven hits on him with my stone sword before i died. I was wondering if he was using hacks for extra hearts because I feel like he would have died by then. You can judge it yourself, heres the link:

skip to the end of the video to see the fight. If he is hacking i'm going to report him.
i have almost no subs so maybe if you like it you can sub.

Full iron reduces damage by 60%. A stone sword hits 3 hearts normally.

A stone sword hits 1 heart per hit on iron armour. So 7 hits = 7 hearts of damage.