Yeah, odd that.
In the context, it seems like it uses zero based partition numbers [0-5], instead of the more common one based partition numbers [1-6]. Remember we're only only capturing the calls to one kernel function with this POC release. It could be that the different M$ engineers that wrote the different functions had different ideas (it wouldn't be the first time the "0 or 1 based numbers" argument would have raised it's head in software development

). The files end up where expected on drives E: and Z:. - go figure.
Pure guess, but I suspect 4D5300C800000001.dat is used to record this title has been installed, and would prevent it being installed again.