That's the right comparison because,

这么比较才对是因为
if I throw now, my probability of winning the game

现在我赢得游戏的概率
is the probability that I hit my opponent.

就是我击中对手的概率
If I wait and take a step, then my probability of winning the game

如果我等一下前进一步我赢得游戏的概率
is the probability that he misses me tomorrow.

就是下一轮对手失误的概率
So I have to compare winning probabilities with winning probabilities:

所以应该这样比较获胜率之间比较
I have to compare apples with apples, not apples with oranges.

应该拿苹果和苹果比而不是苹果和桔子比
Everyone see that? Okay, so let's put that up.

大家都明白吗
So the same assumption:

相同的假设
assuming no one has thrown,

假设还没有人投出海绵
if i knows (at d) that

如果我在d点知道
j will shoot tomorrow (at d--1),

j接下来会在d-1点投出