 <p>Look at the file you give with the <code>excelFormat</code> item I would guess it is due to the following line in it:</p> <pre><code>&lt;Table ss:ExpandedColumnCount="7" ss:ExpandedRowCount="68" x:FullColumns="1" x:FullRows="1" ss:DefaultRowHeight="15"&gt; </code></pre> <p>You can see that it has a mention of an <code>ExpandedRowCount</code> which is set to 68. A quick search for <code>&lt;Row</code> in that same file gives 44 results. If you add your 22 lines this brings you up to 66 which is only 2 short. I'm not quite sure where this goes wrong since there is still a difference of 2, but I'd guess that this is your issue. Try changing the ExpandedRowCount attribute to be something higher and test again (with less than 22 items, exactly 22 items, and more than 22 items). </p>