By default the Query Results list is set to return a maximum of 2,000 objects. If you want to increase that number you can easily do so by using either the IIS management console or editing the web.config file directly.
If you want to use IIS then navigate to the SCSMWebContentServer website, expand that and select the ServiceHost application. Double click on Application Settings. Then click Add… and create a new application settings called ‘MaximumInstanceCount’ and set the value to whatever you want it to be. Keep in mind that setting a high number here will (a) result in potentially long query times for portal users and (b) could negatively impact database performance.
If you want to edit the C:\inetpub\wwwroot\System Center Service Manager Portal\ServiceHost\web.config file directly you can do so by adding this bit of XML: