Okay, so I understand that if you were backing to liability it changes dramatically. In the above example, if you are just letting someone back each selection for 1 unit regardless of liability and exposure to bank, would the figures then be approx. correct?

My thinking was that they have backed 20 winners, which including there 1 unit stake has returned 85 units total to them, this would mean I have paid them 65 units of my own bank. Therefore I am down 65 units on paying out the liability to those bets, but then have taken there 1 unit on the other 80 bets, therefore 80 units up before commission.