A font developer can assign any glyph to any class, each identified with an integer called a class value. A Class Definition table (ClassDef) groups glyph indices by class, beginning with Class 1, then Class 2, and so on. All glyphs not assigned to a class fall into Class 0.
Does "all glyphs not assigned to a class" literally mean every other glyph in the font
or every other glyph in the coverage table
or something else?