Preview of backuped data is sorted alphabetically and not by date. It can be changed in file /includes/acp/acp_database.php:438
$backup_files[gmdate("d-m-Y H:i:s", $matches)] = $file;
$backup_files[gmdate("Y-m-d H:i:s", $matches)] = $file;
Or maybe better (without changing date format) using custom sort function in line 448.