Except that in the current context, the {...} meansrepetitions ;)

Please correct me if i am wrong but doesn't this

identifier ::= letter | '' { identifier-char }
identifier-char ::= '' | letter | digit

mean that an identifier can only have one letter if it starts with a letter not an underscore, in the tests the function names (which are id identifiers) have names like 'avg' which would seem to violate this.
I may have the wrong end of the stick here so please correct me if i'm wrong.