You may often come across situations where you wish to change the severity of an override. Classic example is the infamous 'Script or Executable Failed to run' with a severity of Warning. In large environments, especially where the old school technique of rebooting servers regularly for no particular reason is in place. :-)  One technique I have recommended to my clients is to rather than disable this rather noisy alert, rather tempting, just modify its severity to informational. Although these errors must be dealt with and do occur in large numbers, they definaltey are not urgent. Most of them are traced back to insufficient reosurces, improperly configured WMI or Corrupt Perfmon  objects.

So back to the override, the override is numeric and its value for informational is 0 whereas the default for warning is 1.

0 = INFORMATIONAL
1 = WARNING
2 = CRITICAL

Thanks to Eric Kamor for the information.