Putting timing components back together and have extra O-ring

[Syazwi]

Help needed!

I ordered ECS timing chain kit - ultimate assembled by ECS. My local tech has put everything back together and cannot find where one of the o-rings supplied is supposed to go.

https://www.ecstuning.com/b-victor-r...1421702905~vr/

the oem kit comes with this part number

https://www.ecstuning.com/b-genuine-...ket/n90362001/

The description mentions it to be the lower tensioner gasket. Looking at the lower tensioner we cannot figure out where the o-ring is supposed to go.

I think its item 36 on the attached image but we still cannot figure out where it will go. Behind the tensioner? on the engine block?

Thanks!