This is the 6984th most frequent Korean word.
적잖은
"Quite a few" or "considerable."
In this sentence, '적잖은' emphasizes the substantial impact or seriousness of the shock experienced.
그 일은 나에게 적잖은 충격을 주었다.
That situation gave me considerable shock.
Here, '적잖은' is used to stress the substantial amount of effort required to complete the task.
그 프로젝트를 마치는 데는 적잖은 노력이 필요했다.
Completing that project required significant effort.
In this context, '적잖은' points out the large quantity of attendees at the event.