not a bit= not at all
-Do you mind if i smoke here?
-Not a bit.Do,please.
一点也不.请吧.
not a little:
ad.不少(很多)
Examples:
1.I am so sorry to give you not a little trouble.
真抱歉给你添了这么多麻烦.
2.She was not a little (ie very) worried about the expense.
她对那笔开支相当苦恼.