not (...) until 8:00

[Seiichi Myoga]

Hi,

Do you agree that both (2a) and (2b) work in the blank (X)?

1. Speaker A: What time will Bill arrive?
Speaker B: (X)

2. a. I don't think until 8:00.
b. Not until 8:00, I don't think.

Thank you in advance
Seiichi MYOGA

[Mordant]

Both will be understood to have the same meaning.

"Not until 8:00, I don't think" - The use of "don't" here gives it the sense of "unless I'm mistaken." It seems less certain than "Not until 8:00, I think."