The Settings dialog lets you configure global aspects of the monitoring service.
There are several dialogs that are reached by the buttons on the right side of this dialog and which are also accessible via the Settings menu.

Startup Wait Time - When the monitoring service starts, you can instruct it to wait a number of seconds before active monitoring begins. This places less load on the system while it is starting, and also reduces false alarms that occur from the system not being completely started.
Ignore First Actions - To further reduce false alarms, the monitor service can ignore problems found on the very first run of each monitor. After the first run, all monitors will run normally.
Logon As User - This is a very important setting. This setting lets you control which user account is used to run the monitoring service (this is the same setting you can set on each service in the Administrative Tools Services applet). Windows protects system resources (both local and remote) by comparing the access rights of the requesting user against the rights allowed to that resource. You use this setting to select a user that is acceptable for the Windows security policies that are in effect.
CPU Throttling - The monitoring service has advanced CPU throttling built in which works to keep the average CPU usage at or around the value you set. Note that during report creation, the CPU usage will sometimes go above the throttle level, but it won't stay there for long.
Log Files - The monitoring service writes diagnostic log files as it runs. You can control the maximum size for the log file. When the maximum is reached, a portion of the beginning of the log file is removed and then new information continues to get written to the end of the file. Debug logging writes a very large volume of data to the log in a short time--it shouldn't normally be enabled unless needed by Power Admin Support to diagnose an issue.