I read GTD twice now and while I feel that I understand most of the book, the "a to z" filing system for general reference materials remains a mystery. What I'm picturing is one file folder for each letter: a, b, c, d, e, f, g, h,... w, x, y, z. And if you get a bank account summary where no action is required but that you want to file, you would then file it into the "b" file, for bank.... or is the "r" file for Royal Bank (the name of the bank)??? This is what confuses me. I can see myself filing similar files in various different letters. Another examples, let's say I've paid my phone bill and want to file it. Do I put it into "p" for phone or "t" for telephone or "v" for Virgin (the name of the telephone company)????

Perhaps I'm completely misunderstanding the system. Can someone please clarify this A-Z system and how exactly to use it without confusion? Thanks.