For features such as SVN polling a default value is required. If job will only be started manually, this field is not necessary.
There are 4 special default values which will be evaluated at runtime:

• FIRST - will evaluate to the first item in the drop-down that would have been presented had the build been executed manually.
• LAST - will evaluate to the last item in the drop-down that would have been presented had the build been executed manually.
• RELEASE - will evaluate to the version marked as RELEASE in the repository metadata for the configured artifact. The versionFilter even if defined is ignored for this default value.
• LATEST - will evaluate to the version marked as LATEST in the repository metadata for the configured artifact. The versionFilter even if defined is ignored for this default value.