how do you set the time on the cooker? power was switched off temporarily,then I set the time by pressing the - and + buttons, while holding on the last button on my leftbut on finishing setting,the time reverted back to original e.g. if the time showing is 12 ,and actual time is 2pm,set it to 2pm,but as soon as my hand is off the button,it reverts back to 12 o'clock.