Martin,
Until 4.10 included, the Number field did not work at all with xs:integer. If you set the datatype as xs:integer, the field would revert to a plain input field (text field) instead of the Number field.
With 4.11, the Number field binds to xs:decimal as well as xs:integer fields. So the with should now be the same in both cases:
https://github.com/orbeon/orbeon-forms/issues/2187The Number field does quite a bit more than the plain input field, including formatting:
http://doc.orbeon.com/form-runner/component/number.htmlThis said, you should be able to set the field's width using some CSS.
-Erik