Also this is how wiki notes it: The series is currently published as a weekly digital series, and is published quarterly as 100-page "super spectacular" issues
Batman: Legends of the Dark Knight Vol. 1 (Legends of the Dark Knight #1-5) Batman: Legends of the Dark Knight Vol. 2 (Legends of the Dark Knight #6-10) Batman: Legends of the Dark Knight Vol. 3 (Legends of the Dark Knight #11-13, 100-Page Super Spectacular #1) Batman: Legends of the Dark Knight Vol. 4 (Legends of the Dark Knight 100-Page Super Spectacular #2-4)
And found this breakdown on Worldcat (It's fun how the chapters are not chronological) Vol. 1: "Originally published in single magazine form in Legends of the Dark Knight 1-5."
Vol. 2: "Originally published in single magazine form in Legends of the Dark Knight 6-10 and online in Legends of the Dark Knight Chapters 16-29, 41."
Vol. 3: "Originally published in single magazine form in Legends of the Dark Knight 11-13 and Legends of the Dark Night 100-page Super Spectacular 1 and online in Legends of the Dark Knight Chapters 30-37, 42-50."
Vol. 4: "Originally published online as Legends of the Dark Knight digital chapters 38-40, 51, 53-65, 69."
Vol. 5: "Originally published online as Legends of the Dark Knight digital chapters 66-68, 70-84."
https://www.goodreads.com/series/2041...-
Should this series be kept?
https://www.goodreads.com/series/1541...
The latter collects the issues on the former, though from #13 onward it is not exactly clear which is collected where.