some is to few as most is to many. It is unidirectional as there are times when you have some, but not few. However, there are no instances in which you have few, but not some.

Remember, some ranges from 1 to all, few ranges from 1 to less than half of the total. Let's say you are a congress person and you are trying to get votes to pass a piece of legislation. If someone asked you how many votes you were going to get and you answered "Some", you would be correct wether the vote passed or not. If you got 10 votes but needed 50, you would still have "some". If you got 51 you would still have "some" votes.

Consider another case where you are asked the same question by a colleague and you answer "I am going to get few votes". In this case if you got 10 votes and needed 50, you would be correct and have "few". However, if you got 51 votes and your bill passed, your colleague would be confused why you said you were going to receive "few" votes when you clearly had enough.

Of course it wouldn't be an outright lie, but you could not infer a majority from "few" whereas a majority is possibly "some" of something.

That may have been a little long winded, but essentially the idea is that in all cases that you have "few" you have "some", but there are cases in which you have "some" but not "few". Think of the arrows again as sufficient → necessary relationships. Some is sufficient for "few" and "few" is necessary to "some".