So I assume this changed with the addition of the compiled books view, but there used to be a part of the table of contents that said something like “viewing 1-10 of 56”. I loved this because I could tell at a glance how many chapters something had, and compare it to my tag, which I save along the lines of “Dungeon Runner (115)”- if it has gone past chapter 115, I read and update the tab. How else can I see the chapter total without clicking further in? Speed and simplicity are key here.

I know what you mean by the different total numbers showing on the Volume tag. I think that for now, the next best method is to go to the last page of the Volume you're currently adding to verify the chapter numbers.