It's really not that big of a deal. The only reason they want you to write that letter is so you're not just taking random bird courses to boost your average.
So as long as you have a central theme to your focus electives (like a minor or at least a generalized, clear plan) then you're good. Even if you don't, I suspect they wouldn't care if your plan was something that was a real stretch of the imagination to believe, like taking Enviro Sci, Econ, and History, and Japanese courses because you have an interest in the history of economics of environmental sciences in Japan.
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