Use 'mean to say' when you want to confirm or clarify the intention behind someone's words. When you said that, did you mean to say that you're leaving the company?
Pro Tip 2/3
Expressing Uncertainty
'Mean to say' is useful when rephrasing something you've said to make it clearer. I mean to say, it was not a mistake but a learning opportunity.
Pro Tip 3/3
Seeking Clarity
Ask 'Do you mean to say...?' to understand others better when their statement is vague. Do you mean to say that the project is on hold?