What does it mean when a guy says "You're mine' but is not your bf?

Blake54
So I told the guy I like and who likes me in return, that another guy likes me but I do not like him in that way. His response was 'You're Mine." the thing is, he is not my boyfriend we only have been in hangouts and like one date. So what does this mean in guy language?
Updates
+1 y
I also want guy's opinion on this as well.
What does it mean when a guy says "You're mine' but is not your bf?
3 Opinion