Two things grow with 늘다. A skill improves, which is the standard way to talk about language progress: '디디님 덕분에 제 한국어가 이렇게 늘 수 있었어요', 그래서 실력이 크게 늘지 않았어요 'my skills didn't improve much.' A quantity rises — sales, marriages, costs, case numbers, all present in these lines. The manner word is 크게 in five of the eight, so 크게 늘다 'increase a lot' is worth learning as a unit.
Register: the quantity lines read like news reporting