Eberspacher BN4 supplementary timer switch, how to wire it?

Hi
I have a 24 hour timer that im trying to wire in, it has 3 terminals (1) power in, (2) power out when in use, (3) power out when off.
I have connected the power in to the power in on the dash on/off timer switch and the out when on to the out on the dash switch.
Both switches work
But what is the power out when off for? ???
AND will this extra timer just been on/off bypass the shut down sequence?

 

Power out maybe for the cool down cycle on the heater

 

The manuals i have describe a "run on" after the dash switch runs down or is turned off?

 

No ECU, turning it off cuts the pump then the run on is done by some of the safety switches creating a contact but they cool after a few minutes and open cutting the circuit, well thats how i understand it.
Im not going to use the timer as i can see it affecting the run on, think i will flog it