There are two separate behaviors determined in the Miscellaneous section.
The first is a checkbox for reporting to Rebound or Power Key Pro. Rebound and Power Key Pro are produced by Sophisticated Circuits ; these products are designed to detect and reboot crashed machines. When the Report box is checked, QuickDNS server will periodically report the fact that it has not crashed to the appropriate monitor. For more information about this product visit www.sophisticated.com.
The second control in the Miscellaneous section is the Scan Interval slider. The scan interval is the frequency which the server will check its primary data folder for changes to the server's zones. Master Servers for a zone will automatically update when zones are saved, so in most cases the scan interval can be set fairly high. However, if you plan to manually change zone information on a server frequently, or to manually add or remove zones, this should be set to update fairly often.