https://doc.arcgis.com/en/arcgis-online/manage-data/manage-hosted-feature-layers.htm#ESRI_SECTION1_0...
When you enable the options Enable sync (required for offline use and collaboration) or Keep track of changes to the data (add, update, delete features) on your hosted feature layer or hosted table, ArcGIS Online stores information about data changes and offline versions in a change log. This change log grows as changes continue to accumulate. To avoid credit charges associated with a large change log, you can trim it.
There are backend tables for Sync and the 'Keep track of changes to the data' that can grow considerably over time or high volumes of editing.
Toggling sync on/off will remove any replicas (and any offline edits yes to be synced! so use wisely!).
Turning off the change tracking or trimming it will reduce its size. The change log is NOT the same as keeping track of who last made changes to the data (the CreationDate, EditedDate fields etc). It's a table that tracksadds/updates/delete requests and is designed to be used for things like service based webhooks or other change detection.
