This is a video explaining how to change the waste oil timer settings and thermostat.
The timmer has quite a few settings however we use P3 which is the dual timer mode.
To get P3 press the first button and hold until P1 comes up press it again ,P2, will show, press it again P3 will show ,press the middle button to save P3.
You'll need to watch this a few times to work it out.
When you are altering the timer the pump will want to start, so my advice is do it when the heater isn't going until you get the hang of it.
If the heater is under the set thermostat temperature the bypass switch can do the same job as turning it off.