法華義疏 1.176

1.176

「萬二千人俱」下，第二、唱數。即是釋上眾義也。四人以上至萬二千人以還悉名為眾，所以唱多數者，有二種義：一者、阿難若與小人共聞，不足可信；以共多人同聞，方乃可信。二者、少眾圍遶，佛德未尊，多眾所敬方顯德重也。

"Together with twelve thousand people" and so on is, secondly, proclaiming the number. That is, it explains the above meaning of "assembly." Any group from four people up to twelve thousand people is called an assembly. As for why such a large number is proclaimed, there are two meanings: First, if Ānanda had heard it together with insignificant people, it would not be worthy of credence; only because he heard it together with many people is it worthy of credence. Second, if surrounded by a small assembly, the Buddha's virtue would not yet be honored; only being revered by a vast assembly makes the weight of his virtue manifest.