Template:Depth limit inconsistency footnote

In chapter 7, pages 15–16, Shiggy, while talking about the different layers, says, "Anyway, we're finally on to the fourth layer! Only Black Whistles and above can go here. [emphasis in original]" and "The fifth layer! This is the domain of White Whistles alone[.]" This is contradicted in the second volume's chart which says the depth limit of Moon Whistles is the fourth layer and that the limit of Black Whistles is the fifth. The original Japanese releases were investigated and there is no translation error. However, in chapter 23, page 7, Bondrewd states in a conversation with another Delver, "Why bring this up now? It's also for this very purpose that I proposed Black Whistles enter the fifth Layer[.]" This suggests a change in the depth limit has occurred at one point and as such, it is possible that Shiggy isn't aware of it.