Why did my scheduled Journey reach fewer users than expected based on the segment size?

When a Journey is scheduled to start at a specific time, particularly using options like "device's timezone", the actual time the Journey is launched (activated) is critical.

Here's why fewer users might be included than expected:

1. Launch Time vs. Scheduled Start Time: The Journey must be launched before the scheduled start time occurs for users in their respective timezones. The start should be in advance in reasonable time (to allow the journey to calculate the launch segment, if applicable).
2. User Exclusion: If the Journey is launched after the scheduled start time has already passed for some users (because of their timezone), those specific users will be excluded and will not enter the Journey.

Example: A Journey is scheduled to start at 9:00 AM based on the user's device timezone. You launch the Journey at 10:00 AM UTC. Any users whose local time was already past 9:00 AM when the Journey was launched (at 10:00 AM UTC) will not be included.

Recommendation: To ensure maximum reach for time-sensitive scheduled Journeys, launch the Journey well in advance of the earliest possible start time across all the timezones represented in your target segment.