Has it already been confirmed, that these chapters will be released as tankobon 19 in japan, or is that just a guess/for the sake of ordering?
the original series is volume 1-18.
the pilot one-shot that is essentially the test of chapter 1 and 2 combined was released as two books: DAH alpha and beta. they are essentially the same but alpha has Emi and beta has Yakumo on the cover.
with timeshifted it probably won't have numbering just the subtitle "Timeshifted".
perhaps to continue the tradition instead of the volume number it would also have a greek like alpha and beta but this time the letter phi - the same used for phyrexian mana (and the chapters are numbered with this too).
it was uploaded in the main series as it is almost a direct countinuation of the original series, and the readers of the original would have more trouble finding it if it was uploded as a different series. also it's very short so making a seperate entry wouldn't make too much sense.
