Q:

Meaning of 몇 사람 in 성공한 사람은 몇 사람 안 된다

A translation I saw for 성공한 사람은 몇 사람 안 된다 is 

few people become successful people

This surprised me, as I thought that 몇 사람 meant 'some people'; 'a few people'. 
If so, 성공한 사람은 몇 사람 안 된다 would mean something like "Some people don't become successful" - but that implies that many people do become successful, not few people.
Is 'few people become successful people' a reasonable translation? If so, how should I understand ' 몇 사람 안 된다' ? Does it mean that fewer than '몇 사람' actually become successful?

A:

As others said, "X(이/가) 안된다" means "falls short of X".  Usually X is a small number or expression, but it could be a large number.  (I think the expression is more commonly used if the number is "less than expected".)

그 전쟁에서 살아 돌아온 사람이 만 명이 안 되었다.
대한민국의 인구는 오천만은 넘지만 육천만은 안 된다.
가방 무게가 30kg이 좀/살짝 안 된다. = The bag weighs a little less than 30kg.

People usually don't say "몇 (사람)이 아니다", because it's ambiguous (less than a few or more than a few?), unless you're directly contradicting what some other person just said.  For example:

A: 몇 사람 다쳤겠는데.
B: 몇 사람이 아니라 수십 명 다쳤어요. = Not "a few", but a few dozen were injured.

On the other hand, there's an idiomatic expression "하나/한둘이 아니다", which means "not just one (or two)", i.e., "quite a lot":

뒷산에서 귀신을 본 사람이 한두 명이 아니다. = More than a few people saw a ghost in the hill behind the town.
이 계획의 문제점이 하나가 아닙니다. = This plan has multiple issues.
이 계획의 문제점이 한둘이 아닙니다. = This plan has more than a few issues (probably a lot).

