If he is at a team of 20-30 people, that's an easy figure to defend. But when stripe has over 800 engineers (maybe 400 at the time he made that tweet), that seems some kind of major exaggeration.
He's suggesting that his writing (HN, etc) is likely to have encouraged a certain number of people to join Stripe. That's the only context; he's not suggesting anything about effort beyond that, just talking about the value of writing.
He might be going by interacting with team members and a couple dozen saying things like "I got interested in Stripe because of you talking about it" or "I was reading your blog for years, and tipped me towards joining Stripe instead of [other offer]."
The Twitter UI is terrible, but if you scroll up, the context is writing and recruiting. Patrick's claiming that his writing has led to a lot of people applying to Stripe and getting hired, and that seems true given how popular his posts have been.
