'Couple' is a word that in some contexts means two specifically, but in other (informal) contexts means a small number. Generally when somebody describes three or four things as a "couple", they're being informal and a correction isn't warranted.

”but in other (informal) contexts means a small number"

Isn't there a word for that ? I'm thinking of "several". That is what I learned in school (not a native english speaker )

Both "several" and "couple" are applicable. "A handful" or "some" have the same connotation generally, and I'm sure there are many others.