The Magen Avraham OH 132 4 describe the lottery for saying Kaddish. I am having trouble visualizing this. What is if you got an eight, you win. Both those with equal numbers and unequal numbers throw the next lottery for the next tefilah.
The Magen Avraham 132:2 does not describe the technique of the lottery as much as he explains what happens if two people drew the same number. If for example two had drawn the letter ת whose numerical value is 400 the highest in the Aleph Bet, the whole lottery is void and it must be done over again with all participants not just for the two who received the highest number but for those who drew lower numbers. One the other hand, if only one had drawn the letter ת and two others had drawn lower numbers, the one with the ת won and the others can repeat the lottery. In any case, the prevalent minhag today in most communities both Edot mizrach and Ashkenaz is that all those required to say kaddish in unison. Some say that the lottery was done only in a place where there was a dispute in a small minyan of ten. (See Gesher Hachaim Chapter 30:10, Pnei Baruch 34:38 = Mourning in Halacha 39:37) Besorot tovot