Clarify Section 8.

* The phrase "difference between these distances" can either refer to
the conceptual difference (i.e. they hae different semantic meaning)
or to the mathematical difference (i.e. use substraction for the two).
Instead, just remove the sentence since the equations below make it
clear what we're supposed to do here.

docs/draft-alakuijala-brotli-07.nroff

@@ -1277,10 +1277,9 @@ At any given point during decoding the compressed data, a reference
 to a duplicated string in the uncompressed data produced so far has a maximum
 backward distance value, which is the minimum of the window size and
 the number of uncompressed bytes produced. However, decoding a distance
-from the compressed stream, as described in section 4, can produce
-distances that are greater than this maximum allowed value. The
-difference between these distances and the first invalid distance
-value is treated as reference to a word in the static dictionary
+from the compressed stream, as described in Section 4., can produce
+distances that are greater than this maximum allowed value. In this case,
+the distance is treated as a reference to a word in the static dictionary
 given in Appendix A. The copy length for a static dictionary reference
 must be between 4 and 24. The static dictionary has three parts:
 
@@ -1325,7 +1324,7 @@ follows:
 
 The string copied to the uncompressed stream is computed by applying the
 transformation to the base dictionary word. If transform_id is
-greater than 120 or length is smaller than 4 or greater than 24, then
+greater than 120, or the length is smaller than 4 or greater than 24, then
 the compressed stream should be rejected as invalid.
 
 Each word transformation has the following form: