나

as many as / a whole — a surprising amount

Stuck onto a number or quantity, it flags the figure as bigger than the speaker expected: 30종류나 'a full thirty kinds', 24km나 남았다 'still a whole 24 km to go', 몇 개나 받았다 'won quite a few'. It is a reaction to the size, not a neutral count — drop it and the sentence still works but the amazement disappears. The same particle is baked into fixed words like 아무데나 'anywhere at all', 꽤나 'quite', and 역시나 'as expected, sure enough'.

Register: neutral spoken; adds emphasis