If I understand, you are saying that the dipstick on your tractor is not marked correctly and you would like to know what the proper amount of oil for the engine is so that you can change the full mark on the dipstick to the correct place?
A bit of searching indicates that the FX24D uses the Yanmar 3TN84 engine, same as in the John Deere 870 and the oil capacity is 5.1 quarts or 4.8 Liters.