I have actual stats rather than speculation in the article if you read my post.
It's more like 15k users over 24 hours... then usually another 5k. I included full google analytics charts if you're interested.
FWIW I estimated visitor count mostly based on a requests per second metric I had handy from GAE console. Also sanity checked against other similar blog posts like ours to see other people's numbers. I'd say 50K was a good lower bound. It was hard to say but I'd be surprised if it was as low as 15K-20K. In my experience Google Analytics numbers can be really deceiving. Especially when you compare them to other tracking methods, and go "huh?". Or your other tracking methods are messed up. Either way! Lies, damn lies, and statistics, as they say. HN audience probably uses ad blockers a lot more too which could potentially really skew things, unless you're doing GA stuff server-side.
I made a conscious choice to not even track visitor count, which I'll expand on...in another blog post!
Good luck with Polar!
Also, the traffic is not very targeted. A lot of people reading news, but not necessarily early users of whatever you are doing. So traffic dies down pretty quickly.
PS: it's funny to see the bots posting anything that got popular on HN to reddit, and see the smaller peaks of traffic from Reddit the following days.
I think it will be more than 15k users for you in that regards.
To get the correct estimation, one might need to include an integrated pageview component on the app/post or maybe Snowplow.