if he's asking your size, then you know where his mind is. As simple as that.
So is your mind there too, or are you looking for something little more.
Now if its playful flirting than yeah I get it, but if its just right off the bang how hung are you? Give me your stats? Thats hook up talk and nothing more and unless you're looking to have some quick fun then is kinda trashy.
So looking for sex, its all fine and dandy.
Looking for more, playful flirty is more acceptable.
for as size in general I'm more of a size of your heart and mind kind of guy. Though I prefer a guy that is decently endowed, a penis is a penis as long as its 5 inches and up, not to offend anyone 4 and below. Whatever comes with that idea dude will become my idea size.