"Young Master Fang and Young Master Yang please enjoy; Ah Jiu will take my leave!" Even though Su Jiu was here to express his congratulations towards Fang Zhengzhi and Yan Xiu, he knew that in such a situation, as a boy servant, he wasn't qualified to enter.
Hence, after expressing his congratulations, Su Jiu prepared to leave.
But, would Fang Zhengzhi allow Su Jiu to leave just like that? Naturally that wasn't possible, hence, he quickly halted Su Jiu.
"Since you are here to express your congratulations, then let's eat together!" Fang Zhengzhi very generously pointed to the seat beside him.
Yan Xiu looked at Fang Zhengzhi and didn't speak. All along, he was never a person who chose friends based on their social status, else why would he be together with a poor person like Fang Zhengzhi?
Furthermore, today, Fang Zhengzhi was the host. Hence, Fang Zhengzhi inviting a person who expressed congratulations to eat together was within the etiquette.