You have two alerts that you set up. Both send email messages to a list of email addresses (or a list of Users). In other words, the Recipient tab is configured like shown.
The first alert sends a single email to all three recipients. The other email sends an email to each recipient. The Recipient tab looks exactly the same for both alerts. Why is the number of emails sent different?
The difference between the two alerts is most likely on the Event tab. The alert that sends a separate email message to each recipient is configured to Combine multiple alerts into summary notification. The alert that sends one email to the entire list is not configured this way.