1.6 billion users seems too high. When I Google it says 1.6 billion visits but around 400-600 million users. A better comparison would be against the biggest subreddits as that takes into account the ratio of users actually subscribed. That's around 30 million. Assume that 1% stutters, that's 300k. Considering there is a degree of severity to stuttering, people merely curious to look in the subreddit but don't want it in their feed and the people that can't face seeing a mirror image of themselves another decimation of the numbers seem reasonable to me to arrive at 300k * 10% = 30k 30k seems around the right ballpark for expected subscribers for /r/stutter