Price the actual trains, not the city names
Search the official KORAIL booking page for the date, direction and passenger type you will really use. Add the standard-class fares per traveller, including the return if it exists. Different train times or classes can change the total, so the calculator deliberately accepts your live figure instead of freezing a route fare that may later become wrong.
A two-day pass needs two useful rail days
The official visitor pass starts at two selected travel days within a ten-day period. One outbound day and one return day can fit that structure, but buying a two-day pass for only one useful day wastes capacity. Enter the number of separate calendar days on which you plan eligible KORAIL travel; hotel nights in Busan do not count as rail days.
Keep the exclusions visible
SRT, metropolitan railways and temporary tourist trains are not included in KORAIL PASS. Add any such spend as an uncovered group amount so the result shows the complete trip outlay. The same excluded amount belongs on both sides and should never be disguised as a pass saving.