The Validator is pointing to an incorrect value of meta data in the content for the "ncc:files" entry.
<meta name="ncc:narrator" content="DTG" />
<meta name="ncc:sourceDate" content="2003" scheme="yyyy" />
<meta name="ncc:sourceEdition" content="None" />
<meta name="ncc:sourcePublisher" content="RNIB" />
<meta name="ncc:files" content="17" />
<meta name="ncc:generator" content="LpStudioGen 1.6" />
<meta name="ncc:kByteSize" content="2083" />
The given value of 17 is incorrect.