How many rounds of BBL do you need?

Excuse me, could you please elaborate on the number of rounds of BBL that are required? I'm curious to understand if there's a specific number that's typically needed or if it varies depending on the situation or the goals being pursued. Is there a minimum or maximum limit to the number of rounds, or is it more flexible? Additionally, could you also explain what factors might influence the decision on the number of rounds needed? I'm looking to gain a better understanding of the process and its requirements.