Translation:There are two chairs.
@Pól (I can't reply directly to your comment either)
It's a similar idea to that, but counters in Japanese usually make more sense (once you've learned them) and are less esoteric than collective nouns in English ("a murder of crows" or "a business of ferrets" for example).
I think it's more appropriate to think of counters like a unit of measure. We have these kinds of words in English too; "a stick of butter", "8 glasses of water", "50 head of cattle". Counters in Japanese are used similarly, for categories of things. For example, "stick" evokes an idea about things with a certain shape, "glass" can be used to count many different things, as long as they're liquids, "head" is for any large animal but typically farm animals. In the examples you gave, "flock" could be used for both birds and geese (which are also birds). Similarly in Japanese, 本 (ほん) is the counter for "stick-shaped things", 杯 (はい) is for "a glass-sized amount of any liquid", and 頭 (とう) is for "large animals but typically farm animals".
So, in principle, counters aren't too difficult a concept to learn, albeit with a fair bit of memorization.
The "for specific numbers" part that you mentioned is where it gets really tricky though. While the counters themselves don't change depending on the amount of things you have, their pronunciation can vary depending on the exact number of things your count. Typically these fall under the explanation of rendaku (changing consonants from unvoiced to voiced), but there are quite a few exceptions which simply need to be memorized.
(For some reason, I can't reply to your post Trevorist)
Unfortunately, it's just memorization. As someone mentioned in a different exercise, it pays to learn as much as you can, but you'll be fine with just the generic counter つ.
If you know a more specific counter for the thing you're counting, go for it, but don't be worried that Japanese people are judging you for not having memorized all of them. My partner, who is Japanese born and raised, said they learn a few counters at school, at least the ones that appear in the texts they study, but most people will not know all the counters that exist.
Take a look at this: https://en.wikipedia.org/wiki/Japanese_counter_word
Obvs no one in England is going to hold you to a murder of crows, parliament of rooks, or wunch of bankers - that's just literary types having fun.
Perhaps these counts could also be thought of as like "a single," "a couple," "a trio," "a half-dozen," "a score," "a fortnight," etc.- just useful as alternative ways of saying things to keep language emotive, playful, and harder for androids to master.
One is いち or ひと(つ).
Two is に or ふた(つ).
Three is さん or み(っつ).
Four is よん, よ(っつ), or し.
Five is ご or いつ(つ).
Six is ろく or む(っつ).
Seven is なな(つ) or しち.
Eight is はち or や(っつ).
Nine is く, きゅう, or ここの(つ).
Ten is じゅう or とお.
The ones with tsu (つ) are kun'yomi pronunciations (like hito-tsu, futa-tsu, mi-ttsu) which are usually used as counters when counting things by taking off the tsu. When you are just counting numbers themselves, usually people use the on'yomi pronunciations like ichi, ni, san.
二つ is a counter. It means that there are 'two things'.
〜があります is used to say that a non-living object exists. It can be translated as "There are..."
They need to SHOW us the PRONUNCIATION of the words in the sentence !!
perhaps clicking on an icon to show proper pronunciation of the exact sentence shown.
Clicking on a character OFTEN sounds out the WRONG READING.
But having a "show pronunciation" link could add kana for the exact sentence!
It would redwood only a single additional entry to the database, redwood no logic,and ALWAYS be correct for every sentence. !!!
I'd actually prefer, hovering over characters to always pronounce the correct context sensitive reading, but that would be more work. Obviously behind their capability to get sorted out.
BUT a single entry, with kana pronunciation per quiz entry would be EASY and INFINITELY Useful to learners. It would be ALWAYS CORRECT, help comprehending, memory, and he'll or ability to connect spoken to written.
THIS they Should be ABLE and WILLING to do.
It'd a matter of adding a single database field, a show/hide link/text-field on the page, and a one time data entry to transcribe and type in the proper pronunciation for each quiz sentence.
That's ALL it would take.
Until then, JAPANESE course is riddled with too many ERRORS (WRONG readings in the audio of individual characters for various sentences), not enough Teaching, Reference, and Expansion gaps.
Also Clears up the ISSUE of not being able to Discern what's being SAID in the AUDIO.
This is Even MORE USEFUL than simply slowing the audio down (if we can SEE pronunciation, we can back track and figure out the audio). It's also less RESOURCE INTENSIVE than adding additional auto recordings. Plus audio recordings can leave ambiguity as to what vowels are ACTUALLY being pronounced. "Spelling", removes the ambiguity, and helps us with audio comprehension. We couldmore easily pick up on subtle sounds.
Anyway, I MOSTLY use the "comment" link for the PURPOSE of finding the Proper SPELLING/PRONUNCIATION of words/sentences.!
THEN DUOLINGO would actually be doing it's JOB Properly. Users Still a Valuable resource. BUT Not RELIED upon 100% for a Major Piece of almost every sentence/word they teach.
VALUE of course, and user comprehension VASTLY Increased.
Transcription and data entry is a one time thing, taking a little bit of time, but it's also not too difficult.
This is a Rather EASY Solution to a HUGE ISSUE with this course !
And when they do so, they should Also show us if a particular vowel isn't "actually" pronounced/voiced. For example: des(u).