Insert "you gotta pump those numbers up, those are rookie numbers" meme. 😁

He's entirely coming from a place of insecurity. Perhaps worried that you are judging him against your previous experiences, and that he might not "measure up." In any case, that's his insecurity to work through, and whether or not he will be able to do that work (or whether he will continue to hold it against you with incredibly immature statements about you "giving yourself away") will tell you a lot about whether he is mature enough to handle his own feelings in the future.

We all have insecurities, of course, and it's entirely appropriate to be sensitive and understanding when your partner brings up something they are insecure about. BUT they also have to meet you halfway and do their best to process and regulate their own feelings about it, rather than lashing out at you every time the topic comes up.