message: Fix a couple wording problems
diff: @@ -39,19 +39,20 @@ value is to know the factors.
  We accomplish this by using modular arithmetic (where division is undefined),
  and by using massive numbers for the factors and accumulators.
  -A <font color="blue">tails file</font> is a binary file that contains an
  +A <font color="blue">tails file</font> is associated with an accumulator
  +and its factors. It is a binary file that contains an
  array of randomly generated factors for an accumulator. Instead of small
  numbers like 2 and 3 and 7, these factors are massive numbers, far too
  big to display conveniently on a screen. Typically the quantity of these
  numeric factors in a tails file is large--hundreds of thousands to tens of
  millions.
  -The tails file is not secret; it is published as plain text to the world
  +A tails file is not secret; it is published as plain text to the world
  and freely downloadable by anyone. The contents of this file never change.
  Each potential or actual credential issued by a particular issuer is
  assigned an index to an accumulator factor in a tails file. However,
  -only credentials that have not revoked contribute to the value of the
  +only credentials that have not been revoked contribute to the value of the
  accumulator. We will see how this works, below.
  ![tails file and accumulator](tails.png)
  