This tab of the MSBuild action specifies properties for the project.

 

Maximum parallel builds: Specifies the maximum number of processors that will be used for concurrent builds (optional).  A value of * indicates to use all available processors, or a numeric value specifies the maximum number of concurrent builds.  If left blank, builds will be processed sequentially.

 

Property names/values: A list of properties to override (optional).  See here and here for a list of common properties.