Prompts are governed by the engagement schedule assigned to each learner. This schedule allows you to determine how often and on which days learners should be prompted. You have both an account-wide default engagement schedule or can create custom schedules.Currently, engagement schedules can only be set based on the number of prompts that should be sent each day.  In the future, you may be able to send prompts based on learners reaching their target mastery strength by a certain date, or allow learners to set their own prompting schedule.