You know, I haven't verified this, but it's the norm that every chair would be a slightly different dimension, because you'd want to space them all out for everybody's sight lines.
我还没确认这件事，但根据标准规范 每张椅子的尺寸应该略有不同， 因为你需要将椅子错开排列，避免遮住后排视线。