https://www.coupang.com/vp/products/2305665305?vendorItemId=73316296712&isAddedCart=
Today a SSWB KOREA member wanted to buy this KF94 mask from coupang,
but it couldn't be bought respectively before adding another item.
로켓배송 상품
1,300원 이상 추가 시 구매가능
: Rocket shipping item
available when you spend KRW1,300 more

What is 'rocket shipping item'?
We checked out the item page and found it is '로켓제휴' item.
로켓제휴=rocket affiliate

We clicked the icon 'i' and could see what it means.

Let us explain what the korean words mean in english first.
로켓배송=rocket shipping(rocket delivery)
로켓제휴=rocket affiliate
판매자배송=shipping handled by seller
내일도착 = arrival on the next day
무료배송 = free shipping
(19,800원 이상) = over 19,900won
쿠팡 책정가 = price determined by Coupang
배송 = delivery
쿠팡=coupang
일반택배=ordinary shipping (by CJ logistics, Korea Post etc.)
Coupang is a platform like Amazon in US, and they do delivery themselves as well, something like Amazon Prime.
The items on coupang with 'rocket' mark will be delivered by Coupang delivery team itself, and it asks us to add more items. That was why we needed to spend KRW1300 more.
Hopefully this article helps you!