PrintShop Mail may be using a Number variable to read your field, and therefore use it's own numbers formatting, which by default is two decimals, with separators for the thousands.
What you can do is go in your list of Variables (if you don't see it, go to Window->Variables), select your variable, and in the Properties(again, if you don't see, go to Window->Properties), you will be able to customize how the Number shows up. Or, you can simply switch it to Text to take it "as-is" from the Excel file.
Hope that helps!
RaphaŽl Lalonde Lefebvre