some
adjective
1.being an undetermined or unspecified one: Some person may object.
2.(used with plural nouns) certain: Some days I stay home.
3.of a certain unspecified number, amount, degree, etc.: to some extent.
4.unspecified but considerable in number, amount, degree, etc.: We talked for some time. He was heresome weeks.
5.Informal. of impressive or remarkable quality, consequence, extent, etc.: That was some storm.
some的形容词形式有5种，最常用的在这是义项4（表示一些），这个后面一定是复数。
在这篇课文这个句子里some是用的第一项含义，表示某个，不具体的一个。Some person may object. 是它的例句，可能有人会反对，但是不确定是哪一个，只能说某一个。
unit是可数，但是这里就是要说某个更大的单位/个体