To burn to a single-layer disc (DVD5), you can try the following steps:
1. Adjust the Output to DVD5 on the main window in the Title section.
2. Ensure that the “Writable media (DVD-5) size” is set to 4300MB, which is the default for DVD5 burning in most cases, under DVDFab Common Settings > Drives > DVD Write.
If it doesn't help, please contact the support team and provide your DVDFab log files for assistance.