OpenXML stylesheet corruption - openxml

Question

I'm getting an error on this (formatted for readability) OpenXML stylesheet at column 153, which seems to be the '.' in the 0.0% format identifier. Can anyone see what is wrong here? If I remove the numFmts then the issue goes away.
<?xml version="1.0" encoding="utf-16"?>
<x:styleSheet xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
<x:numFmts count="2">
<x:numFmt />
<x:numFmt numFmtId="164" formatCode="0.0%" />
</x:numFmts>
<x:fonts count="2">
<x:font>
<x:sz val="11" />
<x:color rgb="000000" />
<x:name val="Calibri" />
</x:font>
<x:font>
<x:b />
<x:sz val="11" />
<x:color rgb="000000" />
<x:name val="Calibri" />
</x:font>
</x:fonts>
<x:fills count="1">
<x:fill>
<x:patternFill patternType="none" />
</x:fill>
</x:fills>
<x:borders count="1">
<x:border>
<x:left />
<x:right />
<x:top />
<x:bottom />
<x:diagonal />
</x:border>
</x:borders>
<x:cellXfs count="3">
<x:xf />
<x:xf fontId="1" applyFont="1" />
<x:xf numFmtId="164" applyNumberFormat="1" />
</x:cellXfs>
</x:styleSheet>

Answer 1

It's the empty <x:numFmt> element in the line above that's the cause of the issue. The numFmtId and formatCode are required elements within that element.
The schema from ECMA is:
<xsd:complexType name="CT_NumFmt">
<xsd:attribute name="numFmtId" type="ST_NumFmtId" use="required"/>
<xsd:attribute name="formatCode" type="s:ST_Xstring" use="required"/>
</xsd:complexType>
It's worth trying the OpenXml Productivity Tool in situations like these. It will validate files as well as backwards engineer code from a valid file. In your case you'd get something like this: