Umm, I think the default is 0. I just tried creating a new election and look at the Oval/Box tab in the Ballot Options dialog.
1 only moves it in one for me. This can be a bit confusing if you are also using nonzero box margins. If you make the box horizontal margin 1 for example, then the oval gets shifted over 1/4" plus 1/4" less 1/72", which is almost a shift of two. Could that be what you are seeing?
If anyone else is seeing this or can shed more light, please do.