Yes as soon as your hit refresh, assuming you have over 1511 births, it will be posted on the leader board.

Your rank of 300+ must be off, because I have one game with an oldest villager of 101 and it shows my rank of 65. And in another game my oldest villager was 102 with a rank of 16. You will need to click on refresh each time you want your new rankings. So try that again and see what happens.