Hi
If you set it to default value as 0 will not work.you need to add an attribute xsi:nil="true" to that Number element in the mysceham.xsd file.
1.Open infopath form in design mode.
2.Go to File-> Save as Source FIles..
3.Create a folder in local drive and Browse to the created folder.
4.Click OK.
5.Open myschema.xsd in VS from the Source Files.
6.add an attribute xsi:nil="true" to that Number element.
7.Save the file.