Assuming that’s accurate, it’s a pretty shitty way to put it. “Hey man, just so you know you should owe me for life (and I pay your salary so I decide that), but instead of demanding your unending servitude, I’m going to be a chill dude and let it slide. I’m still going to point it out so you feel worse than you already do and think about it every time you see me or make even the smallest mistake, though. Take care, see you around”.
It’s the kind of response someone would give after reading the Bob Hoover fuelling incident¹ or the similar Thomas Watson quote² and trying to be as magnanimous in their forgiveness while making it a priority that everyone knows how nice they were (thus completely undermining the gesture).
But it’s just as likely (if not more so) the Zuckerberg event never happened and it’s just someone bungling the Thomas Watson story.
¹ https://www.squawkpoint.com/2014/01/criticism/
² https://blog.4psa.com/quote-day-thomas-john-watson-sr-ibm/