Final answer:
Dupin means that the robber knows exactly what the loser knows about the robbery, which allows the robber to manipulate the situation to their advantage.
Step-by-step explanation:
Dupin is referring to the robber's knowledge of what the loser knows about the robbery. This means that the robber knows exactly what the loser knows about the crime. It is an important aspect of the robber's strategy because it allows them to remain one step ahead of the loser and manipulate the situation to their advantage.
In other words, if the loser has limited knowledge about the robbery, the robber can use that to their advantage and control the situation. By having a clear understanding of the loser's knowledge, the robber can make calculated moves and avoid getting caught.
For example, let's say the loser knows that a valuable item was stolen but has no idea who stole it or how it was done. The robber, who has inside information about the crime, can use this to their advantage by staying one step ahead, planting false evidence, or creating distractions to divert attention away from themselves.