"He doesn't quite know what to do."
I'd assumed that the sentence above means "He never has the least idea what to do" until I came across the website saying that "quite" here only modifies "know" and only makes the meaning less strong. So they translate the sentence into something like he kind of knows but isn't sure enough what to do.
I'm confused. There's a big difference between the two. Which does it mean? Thank you.