dbca DB_UNIQUE_NAME?

I generated a dbc file with dbca and use it as a template to create other dbs with "dbca -silent."   I wanted to make sure I was not going to collide with other db files that were already being used on a host, and I see this variable is used to assign values to directory names, {DB_UNIQUE_NAME}.  How does "dbca -silent" assign the value for that variable?  Thanks.