Welcome to the Candy Crush Saga Community
Do you have a question or need help with your game? Ask the Community.
Couldn't say for sure why this happens, but it happens quite a lot. Normally all you have to do to get your banner (badge) to show the correct milestone is to replay and win the last milestone level.
That is, if you replay and win level 13,000 you should find that your avatars banner updates to the correct level
Thanks for the update @flegs. You are the first person I have read that has had to reinstall their game just to get their Milestone banner to update. Everyone else has just had to replay their last milestone level. I hope this isn't a sign that more people will be affected in this manner.