I looked at the USDA database for "ham" and there are literally dozens of entries.

I think it's very hard to be sure that you're comparing apples to apples (or boneless ham to boneless ham!) due to all the variations. I'd pick whatever sounds like the best description of what you're eating and go with that, knowing that calorie counting will never be an exact science.
BTW, did you know that Fitday also uses the USDA database?