Birthday Blitz! HELP!

So, one of my guy friends, he likes me, and I like him, we are now both 11, his birthday was yesterday, so he turned 11. So basically when he blew out the candles, everyone said: "How many girlfriends will you have?!" so he glanced at me by the second and said "One." and like I said, we both know we like each other, and I need help. Does he want me to be his girlfriend or something? or was it a joke! please help! It would mean a lot if you gave me in detail answers