關於not at all用法的問題?

"at all" is an adverb used with questions and negatives to add emphasis. "at all" can be placed in mid-position and, in some cases, end-position as well.

Where in mid-position, the exact position depends somewhat on the predication.
(1) like adverb of manner, place after the direct object of action verb or the verb (if intransitive).
e.g. They’ve done nothing at all to solve the problem.
He is not looking at all well.

(2) we can use "at all" before or after an predicative adjective (with same meaning)
e.g. Were you at all upset by Kevin’s behaviour?
They weren’t interested at all.

You don't seem at all worried about this thing.
= You don't seem worried at all about this thing.

In both sentences, "at all" modifies the predicative adjective "worried" and they have the same meaning.
("at all" cannot modify the linking verb "seem")

意思一樣

at all 在這裡是副詞.一般來說<副詞>是用來修飾它前面的詞彙.
所以,你的第一句之中at all是在修飾"seem".
你的第二句之中at all是在修飾"worried".