That's not part of a volume. Those are separate volumes. The story itself is split into 5 arcs, which they name Parts. The website also splits volumes into parts because they release the volume weekly in pieces, but when you buy it the file you get for the released book is the entire volume. I...
I basically disagree with everyone here on the name issue. The art itself wrote Rosalind (I checked the raw to make sure), and the name seems perfectly fine.