Because they said i have 3.65 BTC there, but i must put some (little) cash to reach it.... 
LOOOOOOL!
Wait a minute, you've been here in the forum for around 7 years, why does it sound like you're just a newbie? Not to mention that, based on your bitcointalk account, you're probably immersed in crypto well enough, at least enough for you to understand the technicalities of mining, so why the noob question? And you've just logged in to ask this question?
Anyway, that's 99.9% a scam. Come to think of it, you haven't even heard of the exchange, how come you've got that number of BTC in there?