The main futures contract refers to the contract with the largest position. Under normal circumstances, the contract with the largest position has the largest turnover. Because it is the most active contract in the market and the easiest contract to clinch, speculators are basically participating in this contract.
At present, palm oil contract 1905 has the largest position, so palm oil contract 1905 is the main contract of palm oil futures at present. The ordering operation is based on the variety code+monthly contract. Palm oil variety code is p. Therefore, the order in your trading account is p 1905.