When working with enrollment rules for ODP campaigns you may notice that there are emails happening more frequently than expected based on the enrollment rules. An example below shows both the rules used by a customer as a report showing the emails sent from a campaign.
Due to there not being a guarantee that users will have their time zone known when subscribing enrollment rules that count the number of days actually count as increments of 24 hours. So in the use case shown above the user was technically seeing an email every day, but there was over 24 hours between the sending of each email.
For this campaign to send an email every other day as the customer intended they would instead need to have set the "Must not have matched any campaign in the last 1 days" to either be for 2 days or 48 hours.