This progress window is opened by the dialog "Build Cache Index" and is used to display the progress in building the index of a merged cache.
During the process, the names of all immediate subdirectories of the directory specified within the dialog are first sorted like numbers. Then, the subdirectories are searched in the determined order for an index file. For each file found, the full name of its subdirectory is printed to the progress window and the contents of the file is finally included into the merged index.