Your step is configured to build all configurations, so I'm guessing (since you didn't provide .sln/.bld files) that your solution has multiple solution configurations, and the action is building each configuration it finds.
http://www.visualbuild.com/Manual/vs...olutiontab.htm
"Configuration: Specifies the project or solution configuration to build. Choose All to build all configurations, enter a valid configuration name or select one from the list, or enter a regular expression to match one or more configurations (i.e., Debug.* to match all configurations beginning with Debug)."