Every name position in this chart depends on one thing: a table assigning a number to each letter. The Expression, which sums all the letters, depends on it completely, and there is more than one table in circulation.
The table used here runs A to I as one to nine, J to R as one to nine again, and S to Z as one to eight. It is the arrangement published by L. Dow Balliett in 1908 and it is now usually called Pythagorean, a name it acquired long after it was drawn up and which asserts a descent it does not have. Its logic is simply the alphabet counted off in nines.
The rival table is the one Cheiro popularised in the 1920s and is usually called Chaldean. It assigns values by a different scheme, groups letters that Balliett's table separates, and reserves nine, treating it as too sacred to be given to any letter. The name Chaldean is doing the same work the name Pythagorean does, and the two systems can produce entirely different Expression numbers for the same person.
There is no argument in the literature that settles which is right, because there is no criterion by which either could be. The tables are stipulations. Which one a practitioner uses is a matter of which lineage of books they learned from, and a reader given two different Expression numbers has usually met two different tables rather than an arithmetic mistake.
The atlas records the Balliett table because it is the one the rest of these positions assume.