When ArcGIS map services are published on ArcGIS servers, when querying map layers, by default, the maximum of returned records is 500.

Every MapServer object has a configuration (.cfg) file, and this maximum number is set as a property (MaxRecordCount) of the MapServer object.

This property can be modified by the Administrator of the GIS server.

Navigate to the [ArcGIS Server Root] (e.g. C:\Program Files\ArcGIS\server)\user\cfg, open cfg of the target MapServer object (e.g. test.MapServer.cfg) in a text editor and change the value of MaxRecordCount.