How does telesign assign a reputation score to phone numbers?

Since Telesign is so popular with major companies, I feel like someone should know a bit about their black box score system. From my understanding, you get a better score if you are with a reputable carrier, the phones account is a bit older, and you've successfully used that number for MFA. But surely they can't give someone a bad score because they haven't done these things. Are there any other factors that influence the score, in particular, give you a worse score?