When I booked my rental on Trip.com, it said "full tank rental & return," so of course I filled it up. Since my English isn't very good, I assumed it was a full tank rental & return when they said "full~~" or something like that, but when I checked the email, I saw that the "FPO option (pre-purchased fuel and returned without a full tank)" had been added to the rental, costing an additional $50. It's probably my fault for not understanding the staff's suggestion, but it's still frustrating. I fully understood the Korean instructions on Trip.com when I booked, so I hope they don't suggest options that contradict what they say when I rent. The rental and return locations are located within the airport, so they were easy to find. The car with the assigned number was in the airport parking lot, and the key was inside the car. I just had to show the staff my documents and the car when I left the parking lot. When I returned the car, the return process was completed right back at the parking lot, which was convenient. I followed Trip.com's instructions and returned the car with a full tank of gas near the airport. The FPO option on the receipt was included, which was probably my mistake, but it's disappointing. I hope everyone understands this when renting.