This configuration setting controls the value of the $(Configuration) property that is injected into builds being performed by NCrunch.
When no value is specified for this setting, NCrunch will rely on the default $(Configuration) specified in the project file (usually this is 'DEBUG').
Normally, the $(Configuration) property is injected into the build from the Visual Studio IDE. As NCrunch does not track build configurations within Visual Studio, this setting is a useful way to more closely align the NCrunch build with any custom configuration selected inside Visual Studio.
For more information about why this setting is important and the problems it can solve, refer to Project Build Platform And Configuration.