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This is encryption of your TFA keys in your database. The encryption key is on disk in the wp-content/mu-plugins directory. The only bad thing that can happen would be if you deleted the file with the encryption key, and that would mean the keys could not be accessed, and then you would have to disable the TFA plugin in order to login.
Basically it’s an extra security measure: if someone hacks your database, then your encryption keys used for TFA are still secured, so the hacker still can’t guess your TFA codes even if he possesses a full copy of your database.
David