I vaguely remember someone doing this during a conversation in a bar in Japan years ago, and I saw it again in a manga. What does this mean, if anything? I don’t remember what the conversation was about, and we were all drinking so I wouldn’t trust my memory anyway
After searching online, it seems everyone knows that “たけのこニョッキ”, which was a game from a TV program aired Wednesdays at 11 PM from 2003 to 2005? It’s a game where several people call out numbers in order starting from 1, and if they overlap, they lose. And judging by the name, that posture is a growing bamboo shoot. You mentioned it was a bar, and this does seem like a game suitable for a noisy bar, so it’s plausible.