Why not “only several”? What a great question!
This strikes me as one of those errors that a native speaker of English would never make and thus which, when you run across it in a Candidate’s usage, is difficult to explain. I would tend to mark it “Usage” for being unidiomatic, and assess one or two points.
Thinking further, consider the following examples:
a) For many are called, but few are chosen. – Matthew 22:14
b) She made few mistakes. That is, her performance was strong.
c) He made several mistakes. His performance was very good, but not perfect.
I sense a distinction of “directionality” in “few” and “several”: downwards, toward zero, for the first, but upwards from three, for the latter. In b), the teacher, aware of the large universe of possible errors, is commending the Candidate’s performance. In c), the grader, sensitive to any errors at all, emphasizes that the Candidate’s translation was not perfect. Note, however, that “a few” functions exactly as does “several”:
d) He made a few mistakes.
“Only” always adds emphasis, as in one of my favorite sayings:
e) Finding a job is like finding a wife: you need only one.
Thus, to emphasize b), the teacher could have written
f) She made only a few mistakes. (I cannot explain clearly the need here to add “a.”)
However, the grader, to add emphasis to c), would have to change his sentence elsewhere, such as in the verb:
g) His translation was not perfect: he did make several mistakes.
“Few” would not work in g), because its directionality (downwards, toward zero) does not match the grader’s (“upwards”) mindset, which is that the number of errors was greater than two.
Even though “a few” and “several” can both fit in the same context, to me their sense of directionality persists:
h) You asked for suggestions; I have a few.
i) You asked for suggestions; I have several.
In h), the speaker is modestly minimizing the number of her suggestions, whereas in i) she would be emphasizing their existence and, presumably, importance. Thus “only” would fit in h) (“I have only a few”), but not in i).
In a more parochial context, as ATA graders, we might want to express sentiments such as the following:
j) So many linguists work for the Federal government in the DC area,
but only a few have ever joined the ATA.
If this topic is not yet in our IEGS (all 61 pages thereof), I would suggest flagging it for inclusion in the next edition.
Others’ comments and suggestions would be welcome.
– Doug McNeal (李一德), ATA Chi>Eng grader