The property file shows all the possible values in this way. It is like a document written with comments.
When you change a default, you need to uncomment it and restart the deployit server.
For example, the following is from http://docs.xebialabs.com/releases/3.8/deployit/upgrademanual.html
Placeholder scanning in archives (EAR, WAR, etc.) is now disabled by default. To enable it, edit
deployit-defaults.properties and add the following line: