A comparison mode describes how a metric value should be compared against a threshold value. There are three modes to choose from: single, absolute, and relative.
Review the below link for better understanding.
I am not exactly sure about the benchmark condition but I guess you can use one of them (absolute or relative).
The alert system can be configured to trigger alerts based on certain baseline conditions. There is a fair amount of documentation on the subject on our community. Here are some helpful links: