To set the timer job interval for alerts can set by using the setproperty for the property job-immediate-alerts command in stsadm.
Syntax:
STSADM -o getproperty -pn job-immediate-alerts –pv <property value> -url <URL of the Site>
Example:
STSADM -o getproperty -pn job-immediate-alerts –pv “every 2 minutes” -url http://uday
You have the getproperty command listed above, although the correct setproperty command is displayed in your screenshot.