400k in 18 days with 111 theatres that are probably in the biggest cities in America (which have a much higher PTA than say where I live) is actually quite awful. Indie films in those markets can hit 10k / theatre / day if WOM is solid.
But often they don’t. In total grosses for the year is 173rd out of a list of 404. Lots of movies make less money. And remember it isn’t 18 days with 111 theaters, the first weekend was 4 theaters, the second was 20, the third was 111.