Try to be more clear about the header sizes

docs/specification.rst

@@ -140,10 +140,12 @@ Shares
 ------
 
 A v1 or v2 share consists of a header made of the following integers.
-For v1 the values are represented as 4 byte big-endian.
-For v2 the values are represented as 8 byte big-endian.
+The version number is given by the first 4 bytes as a 4 byte big-endian integer.
 
-#. Format version number
+For v1 all other integer values are represented as 4 byte big-endian integers.
+For v2 all other integer values are represented as 8 byte big-endian integers.
+
+#. Format version number (4 bytes)
 #. The size of a single erasure encoded block
 #. The size of all of the blocks for one share
 #. The offset into the share of the start of the first block