Language Point 6

...all be that clever,...(Para. 3)
As we have learned in Unit 2, you can use "that" to emphasize the degree of a feeling or quality. It's an informal use.
Do I look that stupid?

难道我看上去就那么愚蠢吗？
I can't walk that far.

我可走不了那么远的路。
I've done only that much.

我所做的就那么多。
I was that angry I could have hit him.

我十分生气, 简直想揍他。
It isn't all that cold.

天气没有 冷到那种程度。