I'm not entirely sure why it was so important to him.

I'm not entirely sure how I feel about this one.

I wasn't entirely sure she was talking just to me.

Although he wasn't entirely sure what the whole truth was.

I'm not entirely sure whether this is good or bad.

Although I was not entirely sure how much good going there would do.

I wasn't entirely sure how to feel about the book at first.

We may not be entirely sure where it is going.

We are not entirely sure: they may well be back for a few more weeks yet!

I'm not entirely sure what every word means, but they all sound so great.