8
I have been studying the way that custom enumeration labels work
From source2e.pdf I get:
\def\alph#1{\expandafter\@alph\csname c@#1\endcsname}
\def\@alph#1{
\ifcase#1\or a\or b\or c\or d\or e\or f\or g\or h\or i\or j\or
k\or l\or m\or n\or o\or p\or q\or r\or s\or t\or u\or
...