Have not seen this one but i should imagine that if it has 2 probes and they plug in to the device, then plug one in the in section and the other in the out section! if you want to test them, put one in on a heat matt and the other in your room, should give you an in and out temps.
might have got the wrong end of the stick, but if i can help any more just ask!
E.S.R.A.S (East Sussex Reptile & Amphibian Society)Meet 1st Wed of every month at Falmer, pm for details!!
Also on Facebook....search groups for ESRAS!