HOW DOES IT WORK?
For fixed odds prices, the fractional or decimal price indicates the returns on your stake if all elements of the bet come in.
For binary prices, the spread is based on the market either making up at 0 (if any of the elements of your bet don't come in) or 100 (if all the elements of your bet do come in).
For the index prices you will be given different possible make-ups for different parts of your bet coming in. E.g. if you add 3 possible outcomes to your bet your spread will be based on a 100-50-25-0 index (100 if all elements of the bet come in, 50 if exactly 2 come in, 25 if only 1 comes in).
If you add 4 possible outcomes to your bet, your spread will be based on a 100-50-25-10-0 index (100 if all elements of the bet come in, 50 if exactly 3 come in, 25 if exactly 2 come in, 10 if only 1 comes in) and so on.