To verify the data you are getting from SharePoint, drag the data group from SharePoint on to your form as a repeating table and see what the data looks like when previewed or opened.
I would check your field format in InfoPath that the drop down is bound to. It should be a whole number or text type. You also can open up the properties of the control and use the format button.
My guess is the field in InfoPath is a decimal type or something.