Yup, it's actually really simple, I don't know why people make such a big deal of it. When in doubt, overestimate calories consumed. And if this is important to you, when this happens, just make a note to in the future avoid eating mystery foods on a regular basis, and eat things whose amounts and content you control or can trust is reasonably accurately represented. It's always an estimate, so if you're continually not hitting your weight goals, don't be like the fatties and throw your hands up in defeat, you should know what to do to compensate.