This warning only occurs during migrations from Google Drive, and means that the child folder 'XX' has two parent folders, 'YY' and 'ZZ'. Child folders with two parent folders are only migrated to the first parent folder, in this case FolderYY, to avoid duplication. Moving the child folder to the other parent folder at the destination needs to be done manually after the migration.
The first parent source path listed will be the item migrated. If the first source path listed is My Drive, then the item will be migrated to the root path of Documents in the destination OneDrive.