Hai teman! In Indonesian, some counters as "sebutir" can be interchangeable with "sebuah". The latter is used with things, objects (yes, literally means "one fruit", "satu buah"), and the first is used with rounded objects, including eggs, balls. The meaning of "sebutir"? Well, I am not very sure. It seems the literal meaning is "satu butir", "one grain", and perhaps it is also related to "sebiji" ("satu biji", "one seed"), the counter used for small objects. I would really like to know a better explanation about the meaning of those counters or classifiers because it is sometimes difficult to remember the use of each one.
Selamat belajar! :)
Since I cannot find it in English, here some definitions from Wikcionário (Portuguese), and Wiktionnaire (French):
The simple definition is a classifier / counter for small rounded objects.
I hope it helps. :)
It's for small or round objects. The KBBI (kamus besar bahasa indonesia) gives the following examples: rice grains, diamonds, small bullets lodged in a body (yeah, that escalated quickly). Your examples are all much larger than these examples, and I think the correct classifier for them would be 'buah' (the 'se' just means a single one).
As far as small, flat, round things, I think it depends on the object. Potong could be correct, depending on the object. Potong is used for slices. You already have a small, round flat thing in your first list of examples (button, like a shirt button), so butir could also be correct. It depends on the item.
Here's a list of some other common classifier words:
Buah → non-living thing Kuntum → flowers Tangkai → flowers, leaves Carik → papers Lembar → papers Jilid → books Potong → cakes, loaves Pucuk → guns Ekor → animals Orang → people Helai → long, thin and usually flat things Biji → small round things Batang → long, stick-like things