Translating 2 subtitles (TV drama 03:31 and 03:39)
拿手，
means good at， skillful.

literally means i am very familiar with doing so (just like using my hand).

不对，你还有一手。
You are better than that.

Alternative, 江东 is expecting 江南 think outside the box. 江南 didn't realize that and show confusing expression.