Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Jakarta to Rotterdam as you normally would.
For a flight from Jakarta to Rotterdam, you will be flying into Rotterdam The Hague. Rotterdam The Hague (RTM) is just 4.7 km from the centre vof the city. Rotterdam The Hague is the only Rotterdam airport and it handles 0 inbound flights from Jakarta per day. 0 airlines have flights to Rotterdam The Hague from Jakarta on a regular basis.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Jakarta Soekarno-Hatta Intl Airport to Rotterdam The Hague Airport flight would often be abbreviated as a CGK to RTM flight.