I don't rightly know
A fancy way of saying 'I have no idea what I'm talking about.' Usually said by people who think they're clever but are just confused.
'What's the capital of France?' 'I don't rightly know. I thought it was Paris, but I was wrong.'
'Why is the sky blue?' 'I don't rightly know. I thought it was because of magic.'
'What time is it?' 'I don't rightly know. I thought it was 3:00, but I was wrong.'