It is used internally to provide default value for all reports for "Maximum number of rows to retrieve" setting. This setting is defined at each report level to control the maximum number of rows and can be overridden for each report. Once overridden at report level, this setting has no significance for that report as it is only used to default if nothing configured.

This and all other report related similar settings are read from system settings and populated on pxRequestor.pyReportSettings page.

Let us know if you need more information :)