It could be sum of all the chairs -1, could be -2 if the chairs are two per row, could be that the hub where they turn around has a large radius and the spacing

It could be sum of all the chairs -1, could be -2 if the chairs are two per row, could be that the hub where they turn around has a large radius and the spacing of the chairs is close enough of that you don't "pass" them, could be 0 if there aren't any other chairs. I suspect the answer to this is "not enough information", which, I suppose, hints at an applicants requirements gathering thought process?