hi, it could also mean "and to let you know" that is most used at the beginning of a sentence but during a conversation. e.g. "John ate the whole pack of kisses. Mind you he doesn't even like chocolates." like what Marie-Hélène have discussed, it also means something like "Pay attention, because I want to stress my next point." :)

In addition to what Marie said, "keep this in mind" "take note" "this is important"

Hello Nurbek, "mind you" means "pay attention, bear in mind" but it depends also from the context...