For performance reasons, when you view a Custom Report, Matomo (Piwik) will show up to 1000 rows in the first level of a report, and 500 rows for each subtable. All other rows are grouped into a row having the label “Others”.
If you wish to archive all the data, or simply archive more (or less) than the current rows limit, you can override these values in the configuration file config/config.ini.php. For example, to limit all table to 5000 entries, add the following in config/config.ini.php:
[CustomReports] datatable_archiving_maximum_rows_custom_reports = 5000 datatable_archiving_maximum_rows_subtable_custom_reports = 5000
Note: You can also change the number of rows for Matomo standard reports.