This applies to Stoves gas Cooker, with high level Hood and Grille as illustrated below:
To adjust the time display, press the two buttons, Cooking time and End of Cooking time, simultaneously and hold down while using the - and + (down and up buttons), on the right to set the time on the digital clock.
If you don't have the instruction manual, I hope the above information is of use to you.
Any comment, please email me at firstname.lastname@example.org
Page started 2 Oct 2012, last amended 12 Nov 2018