The build number of the selected build will be recorded into the variable named COPYARTIFACT_BUILD_NUMBER_(SUFFIX) for later build steps to reference. You can specify that suffix part for that variable here.

If not specified, the source project name will be used instead (in all uppercase, and sequences of characters other than A-Z replaced by a single underscore).

Example:
Source project name Suffix to be used
Project-ABC PROJECT_ABC
tool1-release1.2 TOOL_RELEASE_