Al-Duri is the only transmitter in the canonical ten who appears under two different readers. He carries Abu Amr, through al-Yazidi, and he carries al-Kisai, from whom he read directly. That is why his name on its own never identifies a recitation: al-Duri an Abu Amr and al-Duri an al-Kisai are two distinct entries in the canon, with two distinct chains, and a citation that says only al-Duri has failed to say which one it means. The atlas keeps them as separate rows for exactly that reason, and each links to its own reader. The situation has a mirror on the other side of the scheme.
Khalaf ibn Hisham appears twice as well, but as a transmitter under Hamza and as a reader in his own right, which is a different kind of doubling. Between them the two men account for the only places where the neat grid of ten readers and twenty transmissions folds back on itself. Al-Duri lived at Baghdad in the third century of the Hijra, at the point where material from every centre of recitation was being brought together and compared, and the fact that one man could hold two full readings to the standard the discipline required is a fair measure of what that scholarly world was capable of. There is a further reason to keep the two apart on the page. The two readings al-Duri carries do not descend from the same city.
Abu Amr is Basran and reaches him through al-Yazidi; al-Kisai is Kufan and reaches him directly. Two chains, two cities, two sets of recitational choices, one transmitter. The convention of naming a transmission X from Y exists precisely so that this can be said without ambiguity, and it stops working the moment the second half of the name is dropped.