Aw. I see the confusion. I could have written that more clearly.
Each Theme is ranked from 0 to 5; one is Rank 0, a second is Rank 1, a third is Rank 2, and so on.
I've updated the PDF to rewrite the sections on themes to read:
Theme is the kind of trouble an Outlaw finds themselves dancin’ with. It’s their knack for takin’ life’s punches and turnin’ ‘em into stories worth tellin’. At the start, an Outlaw sets the priority for each of their six Themes, either 0, 1, 2, 3, 4, or 5. Zero means they’re as green as new grass, while five shows a soul weathered by the road, wise to its tricks and turns. The higher your Rank, the more Song you can throw into the mix when it’s time to gamble.
and
Every Outlaw has these themes ranked from zero to five; one trait at rank zero, another at rank one, a third at rank two, and so forth. You’re settin’ the rank for each Theme, buildin’ the song of who you are right from the get-go. However you spread it, you get to shape the kind of Outlaw you are at the start, carvin’ out your strengths, weaknesses, and the kinds of stories you’re most ready to dance with.
Hopefully, that's clearer.