Simplifying the description of the Keccak padding rules
According to Keccak submission 3rd document on page 10, the padding scheme changed from round 2 to round 3.


  We shortened and simplified the padding rule. The new padding rule is the pad10∗1
  rule


In the original specifications on page 3;


  $\texttt{pad}(M, n)$ returns a bit string obtained by appending to the bit string M a single 1 and
  the smallest number of zeroes such that the length is a multiple of n.


In Sponge Construction Functions, The Keccak team  proved that both satisfies 


  the sponge construction offers protection against generic attacks if the
  padding rule is sponge-compliant, i.e., it is injective and ensures that the last block is different from the all-zero block


They changed it because of this rationale:


  pad10∗1 is simpler to describe and to implement than the rounds 1-2 padding rule


In Short, Keccak padding rule evolved during the submissions.