How to do a factory reset to JY-UZS07N8 ?

[King Key]

Hi, I have a JY-UZS07N8 (9" single DIN Android 12 universal head unit) and wish to do a factory reset. I can see the 2 reset buttons (1 on the screen, 1 on the main unit), but this only does a minor reset. The booklet doesn't cover how to do it nor can I see it in any of the menu options.

Any ideas?

Thanks