Anyone know how actions are queued in Marketo?

I was wondering about the mechanism fthat Marketo uses to queue the actions it performs on leads. For example, I recently cancelled a webinar program that already had registrants. The program had a smart campaign that sends a reminder email to the registrants at 10a the morning of the webinar.

However, I deactivated the reminder-sending campaign at 10p the night before, but the reminders were sent out at 10a the next morning. I assume this occurred because the reminders were queued up somewhere and not affected by the campaign's deactivation.

Any insight is appreciated. Thanks