Sorry how much did you say?
Sorry the project will start when?
What exactly do you mean by…?
How did you arrive at the figure of...?
you mentioned.... Could you be a little more specific?
Correct a misunderstanding
I'm sorry, that's not what I meant.
No, sorry, there's been a slight misunderstanding.
Perhaps I haven't explained myself clearly.
Reformulate
Please allow me to explain.
Let me put it another way,...
What I meant was...
What I was trying to say was...