It looks like maybe there are some services/sites that partner with #Authy to provide #2FA based on your phone number (distinct from the more standard TOTP), so if you've got accounts on those sites setup with your phone number and then you setup an Authy account with that phone number, these are already pre-populated. I'm basing that on these two Reddit posts:
https://www.reddit.com/r/2fa/comments/o8izzb/can_anyone_explain_the_difference_these_two_types/
https://www.reddit.com/r/CryptoCurrency/comments/8szsbx/authy_is_an_awesome_app_but_there_is_one_major/