Why isn't here "duzi" and "mali" used, I thought these were the plural forms?
"duzi" and "mali" are for the 'masculine personal plural'. Sandwiches aren't men, they are objects, so they undergo "not masculine-personal plural". And the forms for that plural are "duże" and "małe".
I love how correcting Polish grammar involves reminding us that sandwiches aren't human
Good explanation thank you!
If I were talking about one big sandwich and one small sandwich, would it ever make sense to say "duża i mała kanapki"?
Nope, singular adjectives (even if you used two) need a singular noun.