This setting controls the aggregation function used when calculating the saturation of the hot spot code coverage markers.
As the hot spot markers can only map their intensity against a scalar value, NCrunch needs to aggregate the performance data returned from multiple tests to produce a single performance metric for each line of code. Changing this setting will adjust the way that the performance data is aggregated - potentially making hot spots more or less visible depending upon the data involved.
You should adjust this setting in a way that will allow NCrunch to best highlight the performance concerns for the projects you work on.
When working with projects that have a very high level of test coverage saturation, it may be worth setting the Marker performance aggregation type to Max, as this will more effectively highlight performance bottlenecks for distinctive use cases as opposed to subjecting them to the law of averages.
If you are trying to reduce the overall execution time of a test suite as a whole, setting the value for this option to Total will help you to find individual lines of code that are contributing greatly to execution times across the entire test suite.