Mind you
Definition 1 of 2
Pro Tip 1/3Contrasting Point
Highlights a contrast or exception to what was just mentioned. 
He's very punctual, mind you, his brother is quite the opposite.
Pro Tip 2/3Adding Info
Introduces additional, often surprising, information. 
I love traveling. Mind you, I rarely have the time for it.
Pro Tip 3/3Colloquial Emphasis
Used in casual or informal speech to emphasize a point sharply. 
She's always calm, mind you, when there's chaos she takes charge.