# Size history

> How Grovs records each segment's size once a day, and what resets the history.

Source: https://docs.grovs.io/docs/analytics/segments/size-history

## How it works

- Every day from about 04:00 UTC, Grovs estimates the people and devices in each active segment. The run is spread out over time.
- Each estimate is one point for that date, tagged with the definition it used.
- Archived segments are not measured.
- If a segment is too heavy to estimate, or the estimate fails, that day has no point.
- A point is marked incomplete when part of a window was outside your data retention that day.

## Where you see it

- **Segment page**: **Overview** charts people and devices over time. A new segment shows "Not enough history yet."
- **Segments list**: **People** and **Devices** show the latest point if it is at most 7 days old and matches the current definition. Otherwise the list shows "Size not computed yet". Open the segment for an exact count.

## Editing resets the line

Changing a segment's definition starts a new history line. Points for the old definition stay stored but are no longer shown. Renaming a segment or changing its description does not reset it.