Why is the number of users entering my Customer Journey much lower than the count in a segment with the same filters?

This is a common point of confusion. It comes from the fundamental difference between how an event-triggered Journey enrolls users and how a filter-based segment calculates its audience.

Customer Journey entry

When a Customer Journey uses a trigger-based entry (e.g. user_registered, purchase_completed), it enrolls users at the exact moment they perform that action.

• The Journey listens for the event in real time.
• The user count at the entry point only includes users who performed the trigger event since the Journey was launched and became active. Users who did it before launch are not enrolled retroactively.
• Any further filtering inside the Journey (for example a Condition split) narrows that pool even more, but the starting pool is always limited to users who fired the trigger event.

Segment calculation

A filter-based segment works differently. It scans your entire user base for profiles that currently match the filter conditions (e.g. Country is Brazil and Registration Date is less than 8 days ago).

• The calculation is a snapshot of your audience at a point in time.
• It includes every user who meets the criteria, regardless of when they last did anything.

Why the numbers differ

• The segment shows the total number of users who currently have the right attributes.
• The Journey shows only the subset of those users who also performed the trigger event while the Journey was running.

It is therefore expected that a trigger-based Journey enrolls far fewer users than a segment built on similar attribute filters. If you want to reach the whole existing audience, use an audience-based (segment) entry instead of a trigger-based one.