Are the default item numbers in the same order? At least they are in IE and Firefox:
<ol>
<li>One</li>
<li>Two</li>
<li value="10">Ten</li>
</ol>
UPDATE: The problem is that (1) is list-style-positionset to inside, so the position number is displayed as part of the content of the element, not in the left margin, and (2) you are using a font with variable-width digits.
list-style-position: inside . ? , , , ?