The predicted next SBI upvote is only very loosely connected to earnings over time... like the balance in your bank account is only very loosely connected to your monthly salary. It doesn't tell you anything about how quickly you spend money, or even how much you earn.
This article explains more detail about how pending value balances and upvote delivery work:
https://steempeak.com/steembasicincome/@steembasicincome/value-balances-and-upvote-delivery