The above info comes from
I will spare yall a "I TOLD YOU SO" rant.
First one will be 64 pages, but the other two will probably be a little shorter.
Otherwise, it won't fit on the last tankoubon.
They could lessen the page count on the previous volumes to make the last one, just the last two NEXT chapters, but then it'll only take up half of the tankoubon.
I think 64, 50, 50 and make volume 23 & 24 both little over 220 pages is the most logical solution.
Or... publish the final volume with TONS of filler and addtional material. If the author's willing to add 60 pages to it.