It's a shame that it seems not to be possible to go back from a forum relating to a particular sentence, to the sentence in question. If it were possible, it would be easy to test and answer a question like this one. As it stands, it needs a mod to delve into the database.
- but with a bunch of fives rather than with a couple (of) pairs of socks...
As a native English speaker, I would say "We are buying a couple pairs of socks". I would not say "We are buying two pairs of socks". The sentences both mean the exact same thing, can they both be accepted?
I am also native speaker. A "couple" to me can indeed literally mean exactly two, but it can also mean a fairly small inexact number greater than one. "I have a couple of things to do this evening before I go out". Additionally, I think "couple" should be followed by "of".
In the USA, of is fairly universally omitted from a couple of..., though it's essential in UK English.
Jerry, I seem to recollect that you're from a non-UK/USA country whose English is most closely related to that of the UK. Is that correct?
I concur with your use of couple; here's my personal list of inexact quantities:
- a couple = 2 or 3, maybe 4
- a few = 2 to 4
- several = 3 to 7 [several and seven sound a bit similar ;) ]
- many = too many to estimate at a glance.
Actually, I'm from England (= U.K.); I would agree with your numbering, although, perhaps controversially "a few" for me could perhaps be larger than 4, depending on the size of the objects :-)
"A few grapes" could easily be a dozen, "a few apples" would be 2, 3, 4 as you say, but it's all a bit variable.
"It's language not math" as they say.
"...a couple pairs of socks" is good US English (Duo's variant of English), but I (from the UK) instead have to use "...a couple of pairs of socks" or "...two pairs of socks" (Duo's answer), both equally acceptable in the UK.
So, to do justice to two major variants of English, Duo should accept all three translations.