According to Instagram’s Privacy Policy, even though your phone number is marked as private, it’s used by the service to help you be “found” on the network. So anyone who happens to have your phone number could use it to try and find your personal Instagram account if you have this information included.
What happens after 10k followers on Instagram?
Once you have 10k followers, Instagram will make it easier for you to get people to your website via Stories with the swipe up to link feature. Swipe up is the only way to get a direct link from your Instagram to your other web properties. And, it’s available in STORIES, if you have 10k followers.